Welcome to Gaia! ::

Information about pregnancy tests, how they work, when to use one, and more.


~

Table of Contents

- Post 1: Introduction <--- You are here.
- Post 2: How do pregnancy tests work? [internet]
- Post 3: Pregnancy Test FAQ [internet]
- Post 4: Pregnancy Test FAQ continued [internet]
- Post 5: Brands of pregnancy tests [internet]
- Post 6: Reserved.

Pregnancy Test FAQ [internet]

Courtesy of Pee on a Stick. heart


FAQ


1. How soon can I test? Well, first you gotta know how the test works. Briefly: the home pregnancy test (HPT) works by detecting a hormone called human chorionic gonadotropin (hCG.) When an egg is fertilized, it takes about 6 to 12 days to implant in the uterus, and then it begins to secrete hCG. It takes another day or two for enough hCG to build up and make its way into your pee. So, generally speaking, the earliest you can expect a positive HPT is 8 days past ovulation ("DPO") and the latest would be about 16 DPO. It is possible to get a positive test earlier or later, but not as common. In my experience, if you use a sensitive "early" test (anything that detects 25 mIU/mL of hCG or less) you can test around 12-14 DPO and feel reasonably secure with your results (the later you test, the more secure you can feel in its accuracy.)

If you do not chart or monitor your fertility in any way, and you think you may have conceived, you should wait 19 days (or longer) after having sex to test. Why 19?! Sperm can live approximately 5 days in the proper environment; if the sperm managed to live until you popped an egg, the actual conception could have taken place several days after the sex act that got the sperm there. To make sure you're not testing too early, assume the sperm had very long lives (5 days is considered a very long sperm life) and that conception occurred then. Then allow 14 days for the embryo to implant and develop enough hCG to show up on a pregnancy test (96% of pregnant women will test positive by then.)

Note: some HPT's say "test 5 days before your period is due!" or some such thing. Please note they are assuming a textbook 28-day cycle, with ovulation on Day 14. "5 days before your period is due" thus really "translates" to 10 DPO.

Essentially, you should remember that your high school biology textbook was WRONG. NOT all women have 28-day cycles and NOT all women ovulate on Day 14. For more info on this type of thing, see the Fertility Info section.

Here's an example. This is the textbook-perfect 28-day cycle with ovulation occurring on day 14 (in pink.) 10 DPO and later are reasonable days for testing (in green.) This is the cycle the HPT companies have in mind when they say "test 5 days before your period is due!"

[see website for cycle diagram]

Well, not everyone's body works this way. Here's another 28-day cycle-- but this one has ovulation occurring a little bit later, still well within the normal range. Watch what happens to your (green) testing opportunities!

[see website for cycle diagram]

All of a sudden, "5 days before your period is due!" is way too early for you to expect a positive test! (I tend to ovulate later myself, so by the time the "gold standard" of testing at 14 DPO is applicable, my period is already 3 days late! I needed to use an "early detection" test on the first day of my missed period. A "regular" test would probably have been negative-- even though my daughter is living proof that I was, indeed, pregnant wink

Of course, it works in reverse, too. If you're an early ovulator, you're lucky! Check it out:

[see website for cycle diagram]

In this scenario, you could test even sooner than 5 days before your expected period.

Ultimately, it's important to remember that implantation is a variable thing. You may be able to detect a pregnancy very early on, but then again, you may not! If you can't, don't despair.


2. What's the best test to use? This seems to change periodically! Some tests are well-liked and then a "bad batch" comes out, and some tests are known for being duds but then switch manufacturers and redeem themselves. See the HPT Overview section for current comments on each brand.

If you are trying to detect a pregnancy 13 DPO or earlier, you probably want to use a more sensitive brand. Anything that detects 25 mIU/mL of hCG (English: anything that detects a tiny bit of pregnancy hormone) is good for early testing. See the HPT Overview section to see which tests are most sensitive and the HPT Showdown for a real-life comparison of 15 brands.

Surprisingly, cheap tests purchased at dollar stores or on the Internet are often more sensitive and reliable than expensive store brands. HPT's are like soda: very cheap to make, and marked up quite a bit for retail.


3. Can I reuse a test? No.


4. Pretty please? No! It just plain won't work. (You could try, but the results would not be reliable.) Note: until recently I advocated cutting a test strip in half lengthwise to make one test into 2. I am retracting this suggestion because of several reports of false positives using this method.

The reason you can't reuse a test is because the dye/reagent combo is completely used up the first time. If you look at the pink dye near the wick, you will see that it passes across the stick when it's used. If you use the test a second time, there are simply no chemical reagents or dye left in the test. Even if you add dye with a marker or pen, there is no reagent left to bind with hCG (if it's present.)

To prove it, I took some pure hCG (thanks SO much to my friend, who had some left over following some hormonal treatment!) and put 3 drops straight on a pregnancy test (the "control" test.) Then I put 3 drops on a (negative) test I had once used with breastmilk; I also put 3 drops on a (negative) test I had once used with urine. Here are the results ("control" lines are on the right):



You can see that pure hCG, used on a brand new test, resulted in a positive test. The same amount of pure hCG, reused on a breastmilk test and a pee test, resulted in negative tests. There were simply no chemicals or dye left to work.

Also check out the Fun With HPT's section for an experiment involving test reusage and adding artificial dye.


5. Can I still be pregnant if the test is negative (have a "false negative")? In a word, yes. You could be testing too early (before your baby is making enough pregnancy hormone to be detected by the test.) And some women (this is fairly rare, but possible) never get a positive urine test even when they're definitely pregnant (for some reason the hormone doesn't make it into their urine.) I have a friend who didn't get a positive HPT until 25 DPO! (With her second baby, a test at 23 DPO was negative . . . but a test on 30 DPO was positive. Oddly enough, with #3, her positive test came at only 12 DPO.) If you get a negative test but think you might be preggo anyway, wait a couple of days (giving the hCG hormone time to build up) and try again. It's not over until the fat lady sings-- and your period crashes the party.

If you are not monitoring your fertility in any way (OPK's, charting cervical mucus or basal temperature, ultrasounds) it becomes extra-tricky. There are two parts to every menstrual cycle: from the start of your period to ovulation, which can vary quite a bit in length, and from ovulation to your next period, which is usually consistent in length. (This second half is known as the "luteal phase," and the normal range is 10-16 days. It's normal for your typical luteal phase to vary by a day or two. For example, mine is normally 11 days, but 10 and 12 are not unheard of either. I have also had a couple of longer ones by total fluke.)

Because ovulation can happen at any time, it's possible your egg was delayed for some reason (stress, illness, travel, excitement.) This doesn't mean your period is actually "late" (it could arrive within the normal 10-16 days after ovulation), but rather than your entire cycle was delayed due to a later-than-usual ovulation.


6. Could I have a false positive? Check out The Truth About False Positives for an in-depth look at false positives. Essentially, it is possible, but it's unlikely. If you get two lines, you're most likely pregnant. Exceptions: if you have been taking certain fertility meds with hCG, the test may be picking up the hCG from the meds and not an embryo. Also, some tests develop "positive" lines after the time limit. You should NOT read the test after the time limit (usually 10 minutes, but check the directions that came with the test.) Yes, this means you should throw the test away and NOT dig it out of the trash in three hours to see if a line magically appeared. And, if the "positive" line is gray or looks like a "dent" in the test, it is an evaporation line and not a true positive.

Lastly, if you have been pregnant recently, it's possible that the test is detecting residual hCG. However, if a pregnancy ends early on, it's unlikely that hCG will remain in your system very long, so most women have nothing to worry about here. (It's extremely common for women to conceive immediately following an early miscarriage; the body is "primed" for pregnancy, so to speak, and elevated progesterone left from the miscarriage gives the next embryo a great shot at a healthy implantation. So, most women really are detecting a new pregnancy.)

However, the more hCG you had in your system when the pregnancy ended, the longer it will take to dissipate. HPT's can even detect residual hCG for up to 6 weeks following a full-term birth. It's a possibility you should keep in mind if you get positive HPT results soon after a previous pregnancy ended.

Check the HPT Overview page for up-to-date comments on various brands.


7. What's an evaporation line? Evaporation ("evap") lines result with the test's antibody strip just looks slightly different than the space around it. There is a line of antibodies (usually made from mouse cells) in the Control and Test section. The Control line binds with any liquid and turns pink (or blue, in tests using blue dye.) The Test/Result line turns pink only if pregnancy hormone is detected. If not, the moisture passes over this strip and does not turn pink. It may, however, become more visible when the light hits the moisture on the strip-- it may appear gray, colorless, like a "dent" in the test, or like a "ghost line." It may appear at any time-- as soon as the urine hits it, after a few minutes as the test absorbs the moisture, or after the 10-minute time limit. It may appear when the test is drying, or after it has dried. It may disappear as the test is drying, or after the test has dried, or not disappear at all.

The simple fact is that there is always "something there" that is slightly visible-- it's simply the antibodies on the test that would turn pink in the presence of hCG. When the test becomes wet, or as it dries, or after it dries, the antibody strip may become more visible. Therefore, all tests may have them. It is not a defect; it's just how tests are made.

A real positive is identified by its color (pink or blue, whatever the color of the test's dye is) and its appearance within 10 minutes of urinating on the stick. A line that appears after 10 minutes, regardless of color, must be considered an evap line and is caused by the test's chemicals changing. HPT's are rapid assay diagnostics, which means any results appearing after the "rapid" time limit of 10 minutes are invalid.


8. The positive line is really faint. Is this okay? An HPT tells you exactly one thing: your urine either has detectable pregnancy hormone in it, or it doesn't. The darkness or lightness of a line doesn't mean much. Generally speaking, a very light line can mean there is a small amount of hCG in your urine, and a very dark line can mean there is a larger amount of hCG in your urine. This is why you may get a faint positive at 10 DPO but a darker positive at 18 DPO. However, this is not always true. Tests are all different, and even tests in the same box may differ in sensitivity. Comparing light/dark lines will just drive you nuts. If you see a line in the "results" window, you're preg!


9. I took another test and the line is lighter. Does this mean anything? Should it get darker? Not necessarily. In general, the positive line will be darker when a greater amount of hCG is present in the urine, but not always. Some tests contain more or less dye (meaning there is just more or less color to "stick" to your hCG.) Some tests are more or less sensitive-- even 2 tests in the same box can be different. Also, your urine may have more or less hCG in it depending on what you ate or drank, or how long it's been since you last peed. Food itself does not cause false results, but can affect how much urine you have and how dilute it is. Eating salty chips and drinking caffeine all day will result in more concentrated pee, whereas gorging on watermelon and ginger ale will result in lots of very dilute pee. But an HPT is not meant to tell you "how" pregnant you are. It only tells you if you are pregnant or not. As long as there is a line in the results window, you are pregnant.

Some women experiencing early miscarriages do notice their lines getting fainter or disappearing entirely, but even if your line gets fainter, it is not a guarantee that you are miscarrying, or that anything is wrong. See FAQ 21 for normal levels of hCG and how to properly measure it.


10. I took several tests and got both negatives and positives. What gives? See FAQ 9 above; there are many variables-- concentration of urine, sensitivity of the test. Since true false positives are pretty rare, if you get at least one positive HPT, you are probably pregnant. Wait a couple of days and test again or try another brand if you are suspect. If you suspect you have a true false positive (meaning you did not conceive and still got a positive), please share with us so we can let other women know about that brand!


11. Hey, I got a positive test but my period started anyway! Huh? Since some HPT's are so sensitive, they can detect a pregnancy in its very early stages. Unfortunately, it's estimated that up to 50% of pregnancies are lost very early on. In the past, most women did not even realize they were pregnant-- their periods would arrive on time, or perhaps a day or two late. Now, women testing very early may get a positive test, but experience bleeding almost immediately afterwards. This is an early miscarriage, also referred to as a "chemical pregnancy." It is likely that you did conceive and the embryo implanted for a short time before dying. This miscarriage is "disguised" as a period because the bleeding happens right around the time you would expect your period. Because this is so common, you probably have nothing to worry about, medically speaking, if it happens to you once or twice (although it is still heartbreaking when it happens!) If, however, this happens to you more than a couple times, or in consecutive pregnancies, you should discuss it with your doctor, as this can signal a problem (which can oftentimes be corrected with minimal treatment.)

That said, it is also possible to experience some spotting or bleeding and still have a healthy pregnancy, so don't panic! It may be implantation bleeding (from your baby snuggling in your uterus for a nice long stay!) If you experience bleeding after a positive pregnancy test, you should call your doctor.

See The Truth About False Positives for more information.


12. The line appeared after the 10-minute time limit. Is it still positive? No. You can't rely on any test results that appear after the time limit. There is a reason the tests have a time limit-- and torturing us is not usually that reason wink If a line appears in the "results" window after the time specified in the directions, wait a couple days and test again. HPT's are rapid assay diagnostics, which means any results appearing after the "rapid" time limit of 10 minutes are invalid-- after this time, natural changes in the chemicals may cause lines to appear. (Please don't e-mail me to say this happened to you and you really were pregnant. The odds of having this occur and still end up pregnant are the same as the odds of having any false negative and later detecting pregnancy. In other words, the test is still considered negative; some women testing too early get false negatives.)

See A Cautionary Tale and The +/- Tests for examples of "positives" appearing after the 10-minute mark when the tester (me!) was not pregnant.

See FAQ 7 for more info on evaporation lines.


13. The line disappeared after the time limit! Is it still positive? Please see Current Issues & Alerts for information on this ongoing problem with Answer Early and First Response Early Result tests.

A positive result will generally stay positive for 48 hours. Some very faint lines may fade and become difficult to see, however. Note: sometimes a line will appear briefly as the dye in the test passes over the area where a positive result would show. This is not a positive result.

My suggestion: as soon as urine is applied to your test, set a stopwatch for 9 minutes, 45 seconds. Place the test on a flat, dry surface and walk away. When the alarm goes off, read the test from the same distance you would read a book-- allow 15 seconds to examine the test. If there is a pink line (or blue, obviously, if your test uses blue dye), you are pregnant. If there is no line at the 10-minute mark, you are not pregnant or you are testing too early and there is not enough hCG to be detected in your pee. Note: women who have experienced the current "disappearing positive" phenomenon often had a positive result at the 10-minute mark, only to have the line disappear minutes or hours after that. The vast majority of these women have not been pregnant.

If you really get what looks like a true positive, and it disappears, I suggest calling the manufacturer and asking for their input. They may compensate you for the test as well.


14. Will I get a positive test at the same DPO as I did in my last pregnancy? Probably not. Implantation can occur anywhere from about 6 to 12 DPO (with 8-10 being the most common.) Implantation occurs at a different point for each pregnancy. So, for example, your first pregnancy could have implanted at 7 DPO, giving you a positive test at 9 DPO (it usually takes a couple days for the hormone to make its way into your pee in a detectable amount.) Your next pregnancy could have implanted at 12 DPO, giving you a positive at 14 DPO. It doesn't mean one pregnancy is "healthier" or anything; it's just different! (Like your kids themselves will be smile )

Also, it's important to remember you cannot pinpoint the exact day of ovulation. Even the most accurate temperature and cervical mucus-charting methods are accurate within +/- 3 days. So what looks like 5 DPO on your chart could actually be 8 DPO; what looks like 12 DPO could actually be 9 DPO; etc. (In my experience, most women do find charting accurate within a narrower margin, but strictly speaking +/- 3 days is the scientific guideline. I have used abstinence-only Natural Family Planning for years, trained as a teacher of the method, and associate with many couples "in real life" who use the method as well as many "online people," so "my experience" is rather broad.

Even daily ultrasound monitoring isn't always accurate, because it depends on the skills of human beings to perform and interpret the ultrasound. Anecdotally, I have heard from two women undergoing ultrasound monitoring of the ovaries. Both were told they did not ovulate during their cycles; both ended up pregnant-- one with fraternal twins, meaning not only did she ovulate indeed, but ovulated two eggs at that!

In other words, we speak of "DPO" in a cavalier manner, and for most purposes this is okay, so long as we all realize that it is truly a scientifically-based guess.


15. Do I have to test with my first morning urine (FMU)? Not necessarily. In general, FMU is the most concentrated urine of the day and thus more likely to have built up more hCG in it. If you are testing early (before 14 DPO), the HPT is more likely to detect the hCG in your FMU. After 14 DPO there should be enough hCG to be detected at any time of day. Some women have better luck with second morning urine (SMU.) A good rule of thumb: hold your pee for 3-4 hours (and drink as little as possible!) Then pee in a cup. If your urine looks nice and yellow, it's concentrated enough for testing (see FAQ 16 below for more info on peeing in cups vs. peeing on sticks.) If it looks diluted, dump it and try again later.


16. What are the different types of tests, and how do they work? There are 4 main types of urine-based HPT's. There are midstream tests, dip-strip tests, cassette tests, and a new kind, a cup test.

Midstream tests are essentially plastic sticks with a "wick" on the end. You pee on the wick (the directions will tell you how long to hold the test in your urine stream-- it is usually different for each test, so read first!) The pee then travels across the paper test inside. If two lines appear in the window (either | | or + shaped) you're preggers. One line means no hCG was detected. (If no lines or partial lines appear, your test is defective and you should contact the manufacturer for a refund.) Midstream tests can also be dipped in a cup of urine if you prefer not to pee directly on the stick. Read the directions before doing this because it usually requires a different amount of time than peeing right on the stick! The advantages to peeing in a cup: you can make sure your urine appears dark/concentrated enough to test without wasting an HPT; you can dip more than 1 brand of test in the same urine; you don't risk peeing on the wrong part of the test (like the results window) and ruining it; you have more control over how much urine is applied to the stick, so you don't put too much or too little and ruin the test. (I admit, despite the name of this website, I personally prefer to pee in a cup rather than pee on a stick!) These tests are really just dip-strips inside a plastic handle with a wick.

There are two types of midstream tests nowadays. The "old-fashioned" kind displays the dye in the results window for your interpretation, and the newfangled digital test reads the stick for you and displays the words "pregnant" or "not pregnant." Important: the lines on the digital stick cannot be read the same way as other tests. Two lines DO NOT equal pregnant. Both preggos and non-preggos have seen two lines. Let the words do their job and ignore the lines! See Secret of the Digital for more info.

Dip-strip tests are cheaper to buy and therefore are better for obsessive pee-ers who buy in bulk. As the name implies, these tests are dipped in a cup of urine (again, read the directions to see how long for each particular brand!) and display the result the old-fashioned way (in ink lines, not digital words.)

Cassette tests are flat plastic tests that have a "well" to drop urine into. You pee into a cup and use a dropper to deposit a few drops (read the directions!) into the well. The results are displayed in the same way as the other (non-digital) tests. Doctors use this type a lot because information (name, date) can be written directly on the plastic test with a Sharpie. These tests are really just dip-strips inside a plastic case.

Cup tests are a new, "no-step" type of HPT. You pee into the cup provided, and the cup itself is a test. One line shows up on the side of the cup to confirm it is working properly; two lines mean hCG was detected. I am aware of 3 brands that manufacture this type of test; Home Cup (no information about it), Clear Choice, and Simplicity. One clinical study found that a full 3 out of 6 Clear Choice tests developed genuine false positives. (I bought and tried one-- accurately negative, but 1 ain't a scientific overview.) I have several Simplicity tests to play with; I have used 1 so far. Accurately negative, but developed a "positive" pink line a few hours after the 10-minute time limit-- so, like all tests, the results should not be read after 10 minutes.

The benefits to the cup test are, of course, that it takes a lot of effort to misuse or invalidate the test. If you can pee in a cup, you can use these tests! One woman e-mailed suggesting you keep the pee in the cup and take it to the doctor's office-- that way they can see your positive result and test the very same sample themselves if they desire! Heehee.


17. What's the deal with "the rabbit dying"? Once upon a time, HPT's did not exist. (What people like us did in their spare time we may never know.) To determine if a woman was pregnant, her urine was injected into your ordinary garden-variety (female) rabbit. (Get it? Garden-variety? Rabbit? Like bunnies in your gar-- oh, fine). If the woman's urine contained hCG (pregnancy hormone), the rabbit's ovaries would react by producing little pockets of blood. (These were harmless to the rabbit.) Unfortunately, this was in the day before see-through rabbits, so the only way to see the ovaries was to kill the rabbit, cut her open, and peek inside. So, the rabbit actually died whether or not the woman was pregnant. Somewhere along the line that little detail was lost, however, and "the rabbit died" became slang for "being pregnant."

Hmm. Somehow I don't think "deadrabbit.com" has quite the same ring as "peeonastick.com" . . .


18. My period is really late, but my HPT's are still negative. What's up? For women who chart their fertility: One of the main causes of a delayed period (extra-long luteal phase with high temps) with negative pregnancy tests is a luteal cyst. In a nutshell: when you ovulate, your egg ruptures from a small follicle. This follicle is known as the "corpus luteum" (literally means "yellow body," named for its color, and is the origin of the term "luteal phase.")

Anyway, the corpus luteum produces progesterone. In the event of pregnancy, this progesterone will support the growing embryo until the placenta takes over and makes enough progesterone for itself. Then the corpus luteum shrivels up and stops functioning.

In the event that there is NO pregnancy, the corpus luteum also shrivels up and stops functioning-- ending the luteal phase. The drop in progesterone causes your period to begin.

SOMETIMES, however, there is no pregnancy, but the corpus luteum turns into a small cyst and continues to secrete progesterone long after it's supposed to stop. This is called a luteal cyst, and is responsible for too many false hopes! (Progesterone also causes PMS and pregnancy-like symptoms, such as tender breasts.) If this is the problem, it's simple to resolve (usually a single injection takes care of it) but your doctor needs to see you! Note: this type of cyst is not the same type associated with Polycystic Ovary Syndrome (PCOS.) Women with PCOS are no more or less likely to develop a luteal cyst, and women who develop luteal cysts do not necessarily have PCOS. Luteal cysts do not cause false positive HPT's.

For women who don't chart and simply note the length of each cycle: It's much harder to know what's really going on in your body. There are two parts of a menstrual cycle: Day 1 (the first day of your period) until ovulation (which can happen on any day-- the "Day 14 ovulation" is a myth); this phase can vary widely. (Sometimes women do see some sort of pattern-- for instance, I generally ovulate between Day 15 and Day 19; however, it has happened as early as Day 12 and as late as Day 35! This is why the "calendar rhythm method" of birth control doesn't work-- past cycles can't predict future variation. By the way, NFP is not the rhythm method; it has an efficacy rate of 98-99% when used properly.)

The time between ovulation and your next period, known as the "luteal phase," is fairly consistent. (A normal luteal phase is 10-16 days; whatever yours happens to be, it will probably only vary by a day or two.) Ovulation is delayed by stress-- all kinds of stress, even good stress-- so illness, travel, excitement, or even a random fluke can cause your egg to be tardy. (Note: stress cannot delay your period once ovulation has occurred.) So, if you are expecting, say, a 30-day cycle and you're having negative tests and no period by Day 35, it's possible that you simply ovulated later than usual, and your period will arrive as normal at the end of your usual luteal phase.

So, to use myself as an example again, I usually have 11 day luteal phases (LP's.) This means occasionally I have a 10 or 12-day LP. So my period would be "late" if it hadn't started 13 days after ovulation. Therefore, if I ovulate on Day 15, I would be "late" by Day 28. If I ovulate on Day 19, I'm not "late" until Day 32. My rare Day 35 ovulation meant I wasn't "late" until Day 48!

In sum, if you are not monitoring your fertility in any way (charting, OPK's, fertility monitor, saliva ferning patterns, etc.) there are a lot of cycle variables of which you may be unaware. If your period is later than expected but your HPT is negative, test again a week later. If it's still negative, you may simply want to wait and test again in a week. If you are taking medications (including hormonal contraceptives) or have other issues that would affect a pregnancy, you should talk to your doctor ASAP if you suspect pregnancy, regardless of your HPT results (a blood test may be recommended.)


19. Do evaporation lines disappear? Some do, some don't. Evap lines are simply caused by the moisture making the test's antibody strip more or less visible. (The antibody strip is what reacts with the chemical reagents to form a pink line when hCG is detected.) Depending on how your test dries, the evap line may fade or disappear. It doesn't mean anything-- it's a still a negative test. See FAQ 7 for more info on evap lines.


20. Which tests are more sensitive, ones that measure smaller or larger amounts of hCG? A test that measures a smaller amount of hCG is more sensitive than a test that measures a larger amount of hCG-- so a test that detects 20 mIU/mL of hCG is "better" (more sensitive) than a test that detects 40 mIU/mL. hCG is secreted by an embryo after implantation. The total amount doubles approximately every 2-3 days. A test that is more sensitive can therefore pick up a pregnancy earlier than a test with a higher sensitivity level.

A "regular" pregnancy test usually detects 40-50 mIU/mL. An "early" test will detect 25 mIU/mL or less. Expect to pay more for these sensitive tests . . . unless you buy from a dollar store or online, most of which are surprisingly sensitive and reliable.


21. How much hCG should be in my urine during early pregnancy? hCG, the "pregnancy hormone," is produced by an embryo after implantation. Implantation usually occurs anywhere from 6-12 days after conception. (Conception, in turn, must take place within 24 hours of ovulation; if it is not fertilized, the egg disintegrates about 12-24 hours after it is released.) Once hCG is secreted by the embryo, it is metabolized into the bloodstream first, and within a couple of days, is metabolized into the urine. hCG first reaches the urine in very small quantities, too small for a pregnancy test to detect. It increases daily, however, approximately doubling every 2-3 days. Once a woman is about 12-16 weeks pregnant, the amount of hCG decreases for awhile and then remains stable until birth. hCG remains in a woman's system for several weeks after giving birth (and sometimes for awhile after a miscarriage, depending upon how far along things were.) hCG is measured in "mIU/mL."

Because the range for implantation is so wide, it is perfectly normal for two pregnancies to have very different hCG levels early on. (Implantation will be different for every embryo, so the same woman may have very different experiences from pregnancy to pregnancy.)

Here is a chart showing the "normal" level of hCG. Note: the start of pregnancy is calculated from a woman's last menstrual period, even though she does not conceive for approximately 2 weeks after her period begins. Therefore, a woman who is "6 weeks pregnant" is actually only (about) 4 weeks past conception. It's stupid, but alas, most women have no clue when they ovulated, only when they last menstruated, so that's how they do it . . . also, it's important to note that it's VERY RARE to actually ovulate on Day 14 of a 28-day cycle. It's ironic how so many doctors insist on this "fact," yet "everybody knows" the old Calendar Rhythm Method of birth control doesn't work. Why doesn't it work? Because most women don't ovulate on Day 14 of a 28 day cycle! So, it can be perfectly normal for a woman to ovulate only 10 days after her period, or even 20 days after her period-- or even earlier or later. A baby's due date is calculated based on this Day 14 Ovulation Fairy Tale, which is why due dates are so often very wrong.

[chart transcribed to a different format for this sticky]

Days past conception/ovulation (DPO): 7 days
hCG in mIU/mL (in singleton pregnancy): 0 - 5

Days past conception/ovulation (DPO): 14 days
hCG in mIU/mL (in singleton pregnancy): 3 - 426

Days past conception/ovulation (DPO): 21 days
hCG in mIU/mL (in singleton pregnancy): 18 - 7,340

Days past conception/ovulation (DPO): 28 days
hCG in mIU/mL (in singleton pregnancy): 1,080 - 56,500

Days past conception/ovulation (DPO): 35 - 42 days
hCG in mIU/mL (in singleton pregnancy): 7,650 - 229,000

Days past conception/ovulation (DPO): 43 - 64 days
hCG in mIU/mL (in singleton pregnancy): 25,700 - 288,000

Days past conception/ovulation (DPO): 57 - 78 days
hCG in mIU/mL (in singleton pregnancy): 13,300 - 253,000

Days past conception/ovulation (DPO): 17 - 24 weeks
hCG in mIU/mL (in singleton pregnancy): 4,060 - 65,400

Days past conception/ovulation (DPO): 25+ weeks
hCG in mIU/mL (in singleton pregnancy): 3,640 - 117,000

Home pregnancy tests vary in sensitivity; they range from about 15 mIU/mL to 100 mIU/mL. Because hCG levels can be very low (and still be normal!) you shouldn't worry if it's taking longer than you think it "should" to get a positive pregnancy test. The important thing is not how high your hCG is, but how fast it increases. hCG should double approximately every 2-3 days. Early miscarriages are often identified by the failure of hCG to increase appropriately. (Even then, approximately 15% of healthy pregnancies are slow to double their hCG.)

Twins (and higher multiples) generally see higher levels of hCG (about 20-30% higher for twins, not double.) Interestingly, elevated levels of hCG have also been linked with singleton babies with Down's Syndrome.

It is very very VERY important to remember that HPT's cannot tell you "how" pregnant you are, or how much hCG is in your urine. They are simply a yes/no diagnostic tool. While you may see a darker line on a pregnancy test at 18 DPO than you did at 10 DPO, there are far too many variables for you to deduce anything concrete from the darkness of the lines. Test sensitivity can vary; there may be more or less dye or chemical reagent in different tests; your urine may be more or less concentrated depending on what you ate or drank or when you last peed; the tests may have been stored differently; you may have used more or less urine on one test than another.

If you are concerned or wish to monitor your hCG for proper increase, please do it properly-- under a physician's supervision, with a blood test at a lab-- not at home with a pee-stick.


22. My digital test said "Not Pregnant," but the test stick has 2 lines. Am I really pregnant? The lines on the digital test stick (both Clearblue Easy Digital and e.p.t. Certainty) do not mean anything. They cannot be read like a regular test. See Secret of the Digital for an in-depth look at the digital test and a theory as to why there are two lines.


23. Can using too much or too little pee affect the results? Sometimes, yes. Too little urine and the test simply won't work-- the control line will not appear, because there will not be enough moisture to trigger the chemical reaction. Too much pee and you run the risk of over-saturating the test-- in which case the control line will wash away. (See the importance of control lines now? smile It is impossible to trigger a false positive simply by using too much or too little pee.

It is very difficult to actually render a test invalid with either too much or too little urine (though this seems to be a commonly-toted explanation by HPT phone reps when women complain about problem tests!) See my experiments with under-saturation and over-saturation.

I suggest peeing in a cup and dipping the test rather than peeing directly on the stick, for the reasons outlined in FAQ 29.


24. Can I use Clear Plan Fertility Monitor sticks in the digital HPT (or vice versa)? Officially: definitely not. Unofficially: well, kinda. They look identical, but they measure different things. The FM sticks measure LH (one line) and estrogen (one line); the HPT sticks measure hCG (and , and the estrogen is on the right. On a digital HPT stick, the LH/hCG line would be on the left [closest to the wick], and the control line on the right):

]possibly LH.) Incidentally, FM sticks are interesting in that the estrogen line gets lighter as estrogen increases, whereas the LH line gets darker as it increases (as is the case with regular OPK's and HPT's.)

I did try this experiment. I had my pregnant friend use an FM stick in a digital HPT holder; I also used an FM stick in an HPT holder during a "boring" part of my cycle, and again during my LH surge (ovulation.) Here's what happened (in the pic, the LH line is on the left [closest to the wick], and the estrogen is on the right. On a digital HPT stick, the LH/hCG line would be on the left [closest to the wick], and the control line on the right):



My pregnant friend got the correct "Pregnant" reading on the digital HPT holder. Ovulation tests and FM sticks, which detect LH, will also detect hCG (see OPK-as-HPT for in-depth explanation.) Therefore, the LH appears to be dark/surging due to the presence of hCG. The estrogen line is light, indicating elevated estrogen (as is appropriate during pregnancy.) The dark LH line "tricked" the digital HPT holder into thinking that lots of hCG had been detected and was therefore positive; it also "thought" the estrogen line was the control line.

The middle test was taken during the pre-ovulatory part of my cycle, before my LH surge, BUT close enough to ovulation that my estrogen was starting to rise. (This would be a "High" reading on the FM.) The estrogen line was still dark enough to "trick" the HPT holder into thinking it was a control line, and my LH was low enough (light enough line) that the HPT holder thought I had little to no hCG in my system ("Not Pregnant.") So far, both FM sticks used in a digital HPT holder have given the correct results.

Then comes the downer. The bottom test was taken when I was experiencing an LH surge (dark left line) and elevated estrogen (light right line.) Apparently the estrogen line was too light for the test to believe it was a "control" line, and I got an error on the HPT display telling me to "See leaflet." Now, looking at the "See leaflet"/LH surge test and the "Pregnant"/pregnant test, they look pretty darn similar to me. Why did the test read one and not another? Dunno. But it does demonstrate that while there may be some crossover, the tests truly are different, and to obtain the most accurate results possible (which is important to every woman taking an HPT!) you should not mix and match.

Now, I suspect that the Clearblue Digital OPK may use the same sticks as the Clearblue Digital Pregnancy Test, but I have not yet confirmed this. (My reasons for thinking this: the HPT patent states that the test sticks can measure LH as well as hCG. The test holders, the part that displays the result, are probably calibrated differently to give accurate results, but I see no reason why the sticks themselves couldn't be interchangeable . . . but that's just my guess, not a sure thing.) I did have one woman e-mail me and informed me that her Clearblue Digital OPK stick, used in a Clearblue Digital HPT holder, gave the correct result ("Pregnant"), but remember, this is just one anecdotal report.


25. My HPT was positive, but the urine test at my doctor's was negative. Huh? Urine-based pregnancy tests vary widely in sensitivity. Often a home-based test (HPT) is much more sensitive than the kind your doctor's office uses. (Often doctors or clinics use tests that are sensitive to 50-100 mIU/mL of hCG; most home tests detect a level of 15-50 mIU/mL of hCG. See the HPT Overview for various HPT sensitivities.)

Practically speaking, this usually works just fine. By the time a woman suspects pregnancy and confirms with her doctor, she has usually missed her period, is farther along in her pregnancy, and has higher levels of hCG in her urine-- so a less-sensitive test will suffice. On the other hand, women who are trying to conceive and/or monitor their fertility are often much more in tune with their cycles and the potential for pregnancy, and therefore test earlier with more sensitive tests. So this scenario is actually fairly common. Because HPT's are extremely reliable, you should consider yourself pregnant following a positive test. Your doctor should retest your urine again in a few days, after your hCG has had time to increase.


26. My test developed a line, but it's going the wrong way. Or it's in the wrong place. Or it's the wrong color. Is it positive? No. If your test develops a line but it's not in the proper place for a "positive" result, the test is negative. A true positive line is caused by the chemicals and dye "sticking" to the antibody strip in the test. This antibody strip is in the "proper" place. If the chemicals and dye don't stick there, the result is negative.

It is common for a test to develop a line where the wick (the dipping/peeing end) meets the cellulose strip (the smooth white test area.) This is because the dipping end contains a "sandwich" (two strips with the dye/reagent in the middle) and is much thicker than the cellulose (thin, smooth.) The difference in thicknesses sometimes makes residual dye pool in that area. This can also happen when less urine is applied to the test (not enough to make all the dye cross the test.) This is still a negative result. These lines can usually only be seen when a test is disassembled or when using a dip-type test rather than a test encased in a plastic handle.

Sometimes a test will develop some streaking as the dye crosses the window, looking like a wrong-way line, like this:



This streak will likely fade or disappear after awhile. Even if it doesn't, the test should be considered negative. If you are not sure where a positive result would appear, read the instructions that came in the test box.

If the line is the wrong color, it is negative and/or defective. Again, the chemicals and dye stick to the antibody strip in a very specific way.


27. How long after implantation bleeding can I expect a positive pregnancy test? "Implantation" refers to the embryo attaching itself to the uterus. Sometimes women experience spotting or even light bleeding as the embryo burrows deep into the lining. (Some don't; either is normal.) This process can happen in a day, but in some cases, takes a full 4 days for the embryo to completely attach. Implantation generally occurs between 6-12 days following ovulation/conception, with the majority (over 80%) occurring between 8-10 days past ovulation (DPO.)

Once implantation is complete, the embryo begins producing hCG, the pregnancy hormone. It usually takes about 2-4 days for the implanted embryo to begin producing hCG at a high enough level to be detected by a sensitive pregnancy test. So, if you have experienced spotting or bleeding, and you believe it may be related to implantation, you should probably wait about 2-4 days to test (using a sensitive, early-detection test that measures at 25 mIU/mL or lower. If you are using a test that is less sensitive, allow more time. See the HPT Overview for a list of various HPT sensitivity levels.) It is possible to experience a negative test at this point and still be pregnant; if so, wait another couple of days to allow the hCG to build up in your system to a level high enough to be detected, and test again.


28. Will my urine look different if I'm pregnant? No. The appearance of urine is determined by how hydrated you are (more liquid equals paler pee, less liquid equals darker pee), whether you are menstruating (obviously, blood will mix with the urine, unless you're using a tampon or menstrual cup), whether you have a urinary tract infection (which can cause blood in the urine, or pus, which makes your pee cloudy), or the presence of cervical mucus (an indicator of fertility) or seminal residue.

Now, when pregnant, you may find yourself drinking more (due to increasing blood volume), drinking less if you are subject to nausea, experiencing creamy cervical mucus, or become subject to a bladder infection, all of which can affect the appearance of your pee. However, pregnancy itself won't change what your pee looks like . . . and staring at a cup of pee is definitely not a good way to diagnose pregnancy!


29. Is it better to pee directly on the test, or dip it in a cup of pee? FAQ 16 details the 4 kinds of urine tests (midstream, cassette, dip strip, and cup) and how they are used. Most require that you pee in a cup ("PIAC") rather than pee on a stick ("POAS.") However, with midstream tests (the most common kind) you have the option.

It is my preference and my suggestion that you PIAC rather than POAS; this way you can carefully control how much urine is applied, eliminating the risk of over- or under-saturating it. Also, you eliminate the risk of aiming incorrectly and peeing directly on the results window, ruining the test (ask me how I know this *blush*.) Additionally, you can make sure your pee is concentrated (medium/dark yellow, not pale yellow or clear-- if it's too diluted, you run the risk of a false negative.)

Read the directions . . . usually it's recommended that you dip longer than you would hold the test directly in the urine stream, because there is less force "propelling" the urine up the wick and thus takes more to do the trick. Usually, about 15 seconds is sufficient. If the pee has not begun to cross the test and develop a control line within 3 minutes, you can re-dip the test. (This is not the same as re-using a test . . . this is adding more urine to make the test work the first time!)


30. My blood test was negative. Can I still be pregnant? Overall, blood tests are more accurate than urine tests because your blood cannot be too diluted (like urine) and does not require that your body metabolize hCG into your urine (which some women do slowly or, rarely, not at all.) But, in some circumstances, yes, you can be pregnant without a positive blood test.

There are two different kinds of blood pregnancy tests, known as qualitative and quantitative. A qualitative test measures the quality of your blood: either pregnant or not. The test is much like an HPT, except it uses your blood rather than your urine. It means the laboratory has a pre-set cutoff point for determining "pregnant." In some labs, a level of 5+ will come back as a positive test; in other labs, your blood must have 25+ mIU/mL of hCG. Usually the lab will not tell you what their cutoff point is; they will simply tell you yes or no, just like peeing on a stick. You may be pregnant, but just "a little" pregnant, and the blood test was not sensitive enough to detect it.

A quantitative blood test is much more specific; it measures the exact quantity of hCG in your bloodstream. Non-pregnant women of childbearing age have anywhere from 0-2 mIU/mL† of hCG in their blood (average is about 0.5.) Generally anything over 5 is considered pregnant, though 3-4 is a "gray zone" (a little too much for normal non-pregnant, but not quite high enough to pass muster at the lab.) Peri- and post-menopausal women may have up to 9.5 mIU/mL of hCG. If you have this type of blood test performed, there is little doubt that the results are correct (barring lab error.) Exception: prior to implantation, the embryo does not secrete hCG and cannot be detected. Therefore, it is possible to be in the very early stages of pregnancy and still get a negative blood test.


31. Can I use an expired test? No. The chemicals used in HPT's deteriorate after awhile and no longer function properly. This can cause a totally defective test (no control line), a false positive, or a false negative. Your best bet is to use a newer one!


32. I've heard "a line is a line"-- any line is a positive. Is that true? Sort of. The adage that "a line is a line" is meant to emphasize that all positive results are equal; a darker line is not "more" pregnant than a lighter line. Some women are hesitant to trust a faint line, believing that a "real" positive "should" be darker. (This isn't true.) So, in this vein, yes, a line is a line. In other words, these are all examples of positive pregnancy tests:



BUT I think this phrase gets overused. Evaporation lines are not positive results. Lines that appear after 10 minutes are not positive results. Lines that are only visible under high-powered light bulbs when tilting the test and squinting are not positive results. So, there are some lines that are not "lines," so to speak. Here are two tests with evaporation lines. These are negative tests:



And here is one that is the proper color, but appeared after the 10-minute limit. This is a negative test:



So, I would prefer to modify/clarify the "old saying" to read: A line is a line, so long as it is the proper color and appears during the 10-minute time limit.


33. I read online that I can pee on dandelion leaves and they will develop red blisters if I'm pregnant. Is this true? I didn't make this one up, I swear. In case you're not up to speed (up to weed? wink ) this statement has turned up on trying-to-conceive (TTC) message boards across the Internet:



As I told those who e-mailed me, I wouldn't be completely surprised if something happened. An ancient Egyptian papyrus recommends that women urinate on barley and wheat, and if they grow, it means she is pregnant (and furthermore, it can predict her baby's sex-- barley growth is a boy, wheat a girl.) In 1963 someone actually tested this and found that about 70% of the time, pregnant urine does promote plant growth (though not sex-specific to the baby.) Non-pregnant female urine and male urine did not promote plant growth. So, overall, the notion that pregnant urine may react with plants is not a new concept.

And so, in the interest of science . . . I peed on a weed. I took a pregnancy test and ovulation test as a "control." I am not pregnant and not ovulating. I observed the dandelion leaves at 10 minutes and 1 hour as specified in the "FAIL SAFE TEST!!" instructions. The leaves looked . . . wet, and nothing else happened. I repeated the experiment on leaves from a completely different dandelion, just to be sure. Also nothing. The leaves were freshly picked so they were not dried out. So far, so good-- non-pregnant, non-blistered leaves.

A few days later, I had my newly pregnant friend try it out for me. We calculated from a blood test she had awhile ago that she had about 40,000 mIU/mL of hCG in her system when she peed on a weed. (For comparison's sake, a sensitive HPT usually detects 25 mIU or less; the least sensitive commercial HPT detects 100.) She took a pregnancy test as a control-- very positive. Again, we used leaves from 2 completely different dandelions, freshly picked. We observed them at 10 minutes and 1 hour. And . . .

. . . nothing. Apparently the "FAIL SAFE TEST!!" can be failed. So unless we happened to get a bunch of defective dandelions, it appears the dandelion test does not work.

I also researched this concept online, and found no mention of it beyond women repeating or re-posting the original message above. You might have better luck reading tea leaves instead . . .


34. I'm breastfeeding. Can that affect my pregnancy test results? No. While lactating women do produce various hormones, none of them cross-reacts with pregnancy tests. A breastfeeding woman can use a pregnancy test and expect her results to be just as accurate as a non-breastfeeding woman. Using urine, that is. If you dip a pregnancy test in breastmilk you may obtain a false positive result. Stick to pee and you'll be fine.


35. Can I get a false positive if my pregnancy test touches my ovulation test? Yes! Ovulation predictor tests (OPK's) contain different antibodies than pregnancy tests (HPT's.) If you place a wet pregnancy test too close to an OPK (so that they're touching) the OPK can actually contaminate the pregnancy test and cause 2 lines to appear, even if there is no pregnancy hormone (hCG) in the urine. Um, ask me how I know this . . . If you are a weirdo like me and you like to take HPT's and OPK's at the same time for whatever reason, make sure they are placed where they cannot touch one another!


36. Should I take my test apart to see the line(s) more clearly? No. Removing the test from its plastic case changes the test's exposure to air and humidity. Air and humidity affect the manner and rate at which the dye and chemicals cross the test. If you change the environment before the test is finished, you risk drying it out too quickly-- and when a test dries too quickly, the dye may dry in places it would not have otherwise-- making an evap line appear to be a positive result. Additionally, the tests are intended to be used and read while intact. If you think you see a line, but it is so faint you really can't tell, it's probably an evap line and should be considered negative.

Please note: pregnancy tests will work almost anywhere-- the problem is not the amount of air or humidity in general, but changing it in the middle. HPT's are scientific little things, and to achieve greatest accuracy, the environment should not be changed while the test is running.

If you want to photograph or scan your test for posterity (or for posting to your message board buddies for opinions wink ) it can be easier when removed from its plastic casing (to eliminate glare.) If your test is positive, go for it! If it's negative, or you're not sure, you're in a tough spot . . . removing the test from its casing while the test is still wet can "speed-dry" an evap line and make it darker/harder to interpret. But tests are not completely dry at the 10-minute time limit; by the time they dry, the test has passed the 10-minute limit and should not be read. If you think you'll be in conundrum, use a dip-style test or remove the test from its casing before you apply urine.


37. Can I still use pee that's been sitting in a cup for several hours? hCG (pregnancy hormone) does break down and dissipate from urine once it leaves the body. It has a half-life of 24 hours, meaning the total amount will be cut in half for every day it sits out. If you are testing very early when only a small amount of hCG is present to begin with, that half might make a difference (for example, 25 mIU/mL of hCG will be detected with any early pregnancy test. By the time that pee sits out for a day, it has only 12.5 mIU/mL left, and only a very sensitive test may detect it.)

However, most women aren't peeing in cups and leaving it around for days; most women just want to save their FMU (or other concentrated urine) to be used later in the day (may need to purchase an HPT, want to wait for darling dearest to get home from work, may pee in a cup out of preference and then get distracted by a toddler doing a serious number on the poor kitty before you get the chance to dip the test, etc. All very common scenarios.) A few hours is unlikely to make a serious difference in the amount of hCG in your urine, so it's fine to use older pee. Putting your pee in the fridge will also slow the breakdown of the hormone, but I will disavow all knowledge of this suggestion in the event that your husband is grossed out by its proximity to his leftover pizza.


38. I smoked some pot, drank a lot of beer, took Advil, am on the Pill, had sex, and had Chinese food for dinner. Can that affect my test results? No. There is no food*, no alcohol, no contraceptive, and no illegal or over-the-counter drug that can mess up your HPT results, and semen cannot affect the test. The only drugs that can affect pregnancy test results (in the form of a false positive) are prescription drugs that contain hCG (such as Profasi, Pregnyl, Ovidrel, etc.) They are prescribed for fertility treatments or other "female problems." If you are taking one of these drugs, ask your doctor how soon you can use a pregnancy test (different doses require different amounts of time to leave your system, so what works for one woman might not work for you.)

*Food itself does not cause false results, but can affect how much urine you have and how dilute it is. Eating salty chips and drinking caffeine all day will result in more concentrated pee, whereas gorging on watermelon and ginger ale will result in lots of very dilute pee. Very diluted urine during very early pregnancy may result in a false negative. For best results, pee in a cup first and make sure your pee is medium to dark yellow.


39. I am trying to conceive through in vitro fertilization (IVF.) Will my medications affect how or if I can use an HPT? I have been asked this several times, so I am including it in the FAQ, but I'm afraid I have to give a rather cop-out answer: I don't really know. I have had several women send me their HPT's from IVF pregnancies, so I assume it can be done. I do know that IVF medication protocol can vary quite a bit from woman to woman, and that many (most? all?) women undergoing IVF also take synthetic hCG which can cause false positives on HPT's. So, I suggest asking your doctor this question, as (s)he will be familiar with your medications.


40. The directions on my HPT say "for in vitro use only." What does that mean? Short answer: it just means the test is for external use only. Don't cram it up your hoo-ha. Has nothing to do with in vitro fertilization (IVF.)

Long answer: literally, "in vitro" is Latin for "in glass" (thus "in vitro fertilization" refers to the fact that fertilizaton occurs in a petri dish.) It is the opposite of "in vivo," which means "in the living." If a test were "in vivo" it would mean it should be used internally. Which an HPT definitely should not. (And don't ask me what would happen if you tried. Get that look out of your eye.)




[Continued in next post]

Brands of Pregnancy Tests [internet]


Some brands of pregnancy tests and their sensitivity levels.

List of pregnancy test brands.

List of pregnancy test brands from Pee On A Stick.com