POAS ~ OPK FAQ

1. What does an OPK tell me? The female body produces something called luteinizing hormone (LH.) It is present in the urine almost all the time, but increases significantly-- surges-- about 12-36 hours before ovulation. An OPK detects LH in your urine and gives you a positive result when it detects this surge. (If you read this page before and saw "aluminizing hormone," no, you're not crazy. That's what happens when you trust spellcheck and let it "correct" words for you. Hahaha . . . yup, with Aluminizing Hormone, we can all turn into Pepsi cans. If you turn into Diet Pepsi, you're ovulating ;)

If you are trying to conceive, OPK's can help. They are a "crystal ball" that lets you know your egg is probably getting ripe, and the time is right for snuggling! If you are using NFP or FAM, OPK's can be used in conjunction with basal temperatures and cervical mucus to help discern periods of fertility and infertility. A positive OPK does not guarantee that you will ovulate. See this FAQ for details!

2. How do I read the results of an OPK? This is very important: OPK's are not read like HPT's. An OPK has a "control" line and a "test" line, just like an HPT. Unlike an HPT, however, the mere presence of a "test" line does not mean the test is positive. The test line must be as dark as, or darker than, the control line to be a positive result (meaning that a surge was detected, rather than the ordinary amount of LH usually found in your urine every day.) Note: there are now some OPK's that read more like a pregnancy test, where the presence of any second line indicates a positive result. I have not personally seen these. Be sure to read the instructions that come with your tests if there is any doubt what type you have!

Sometimes it is hard to read the results of an OPK-- the test line looks almost the same as the control line, but you're not quiiiiite sure. Some brands develop "half-positive" results where only the edge of the test line is dark (see FAQ 13; this may be a positive result, depending upon the brand of OPK used.) You may find it takes a "practice" cycle or two to learn what a positive looks like for YOU. You may also have clearer results with a different brand of test.

If you're charting your basal temperature and/or cervical mucus, OPK's can help you identify the approximate time of ovulation.

3. Is it normal to see 2 lines all the time? It is very common. Most women produce LH almost all the time, and the OPK will detect it, giving you a "test" line that is lighter than the control line. About 12-36 hours before ovulation occurs, there will be a surge in LH, and the test line will become as dark as, or darker than, the control line. If, however, your test line is almost always positive or nearly positive, it can be indicative of a hormone imbalance. See this FAQ for details. See also Meg's OPK Odyssey for a day-by-day OPK comparison.

4. What if my OPK is positive for several days in a row? It is possible, in a normal ovulation, to have a positive OPK for several days in a row. This is because LH peaks (surges) about 12-36 hours before ovulation occurs, and then dissipates. So, you could theoretically detect this high level of LH with positive OPK's from the time it begins to the time it dissipates-- over 36 hours.

It is also possible that your body is "gearing up" to ovulate, and you have an LH surge-- and then, for some reason (such as stress, illness, travel, or random fluke), your body fails to release an egg . . . then tries, tries again ASAP with another, or overlapping, surge. If you see a positive OPK for longer than 3 consecutive days, your egg is probably just having a little trouble getting out of the starting gate. If this happens to you occasionally, it's no big deal. If it happens a lot, talk to your doctor. (I just play one on the Internet :p)

5. Should I keep testing once I get a positive OPK? Nah. Once you get a positive you will probably ovulate within the next 12-36 hours. You should be able to confirm this with a temperature rise and/or dry up of cervical mucus (remember, even when you're charting your temps/mucus as accurately as possible, it's still only accurate within +/- 3 days . . . so if you get a positive OPK, and ovulate 36 hours later, and have a thermal shift/mucus dry-up 3 days after that, you may have a discrepancy of 4.5 days between the positive OPK and NFP signs! That's the outside time range, you'll probably see the temp shift/mucus dry-up sooner than that . . . but just letting you know it's possible!)

If you don't see corroborating signs of ovulation within a few days of your positive OPK, you may wish to test again and see if the OPK is still positive. This may mean your body just got "delayed" and is still trying to ovulate. If you are consistently seeing positive OPK's without other signs that ovulation has occurred, you should talk to your dr.

6. What if my OPK is positive almost all the time? The most common cause of constant positive or almost-positive OPK's is Polycystic Ovary Syndrome (PCOS.) This disorder is usually characterized by elevated LH (hence the positive OPK's), and is common in women with very long and/or anovulatory cycles.

Don't self-diagnose, though! If you're worried (or just plain obsessed with your pee-sticks ;) call your doct-- okay, okay, you know the drill ;)

7. Can I use an OPK instead of an HPT to detect pregnancy? Check out the OPK-as-HPT section for a detailed answer. The short answer is: an OPK will turn positive if pregnancy hormone is present, but there are many reasons an OPK could be positive. To be sure, you should use an HPT to detect pregnancy and an OPK to detect ovulation. Mixing and matching can get your hopes up.

8. How do I know when to use an OPK? If you've been charting, you probably know approximately when you ovulate each month. Start using your OPK's a few days before you think you may ovulate.

If you have no idea whatsoever, take the shortest cycle you've had in the past 6 months and then use this chart to determine what day of your cycle you should begin testing:

shortest cycle	start testing	shortest cycle	start testing
21	5	31	14
22	5	32	15
23	6	33	16
24	7	34	17
25	8	35	18
26	9	36	19
27	10	37	20
28	11	38	21
29	12	39	22
30	13	40	23

(yes, "5" is supposed to appear twice)

9. Can I get a positive OPK and then not ovulate? Yup! It is possible for your body to "gear up" to ovulate, leading to an LH surge-- and then, for some reason (such as stress, illness, travel, or random fluke), your body fails to release an egg. When this happens, your LH surge will dissipate and your cevical mucus (a signal of fertility) will dry up. Once the stress is resolved, your body will try again. This can happen more than once per cycle. Therefore, there is no way to be sure you ovulated, even if you had a positive OPK. OPK's are most accurate when used in conjunction with fertility charting (NFP or FAM.) That way, a positive OPK can be cross-checked with an increase in basal body temperature and/or cervical mucus dry-up.

10. Should I use first morning urine (FMU) with OPK's? No. LH is synthesized early in the day, and is not metabolized into your urine until later. So, as a rule, you are more likely to catch your surge later in the day. ("They" say you should test sometime around 2-4 p.m., but I've had fine luck at 10 p.m.-midnight.) Using FMU may not be a problem for you, but if you do not detect a surge during the cycle you use FMU, try testing later during the next cycle.

Note: the Clearblue Fertility Monitor is the exception. The FM Monitor does require FMU.

11. I chart my fertility. My chart and my OPK disagree. Which is right? All forms of charting are accurate to within +/- 3 days. Though we use terms like "days past ovulation," we really cannot pinpoint the day of ovulation. In rare cases, it's even possible to have all the signs of ovulation without having popped an egg. It is also possible to have a positive OPK and then fail to ovulate (see FAQ 9.)

Additionally, a positive OPK indicates that ovulation will likely occur in the next 12-36 hours, so it really gives you only a "window" of ovulation, and not an exact day. (The only 100% positive way to know ovulation occurred is to get pregnant! Some women undergo ultrasound to monitor their follicles for fertility treatments, but even this can be flawed. It depends on the skill of the doctor/technician to perform and interpret the ultrasound. I have heard from a couple women who were told, after ultrasound monitoring, that they did not ovulate-- and went on to get pregnant that month!)

Anyway, using the widest margin of error, an OPK may be positive 1.5 days prior to actual ovulation, and temps and/or cervical mucus may not reflect ovulation for a full 3 days after that, therefore leaving a window of 4.5 days between a positive OPK and an ovulatory-looking chart. In this scenario, both the OPK and fertility charting are working the way they're supposed to!

Most often, any discrepancy between your positive OPK and your chart will be within a day or two, and that's fine. If your concern is choosing a day for pregnancy testing, assume you ovulated on the later day-- this way you won't test too early and risk a "false negative" (which occurs when a woman has conceived, but the embryo has not implanted or secreted enough pregnancy hormone to be detected by a pregnancy test.)

12. I never get a positive OPK. Does this mean I'm not ovulating? No, not necessarily. It can depend on how often you test. Most OPK's say to test once a day, around the same time each day. However, it is possible for your LH to surge and dissipate in less time than that, so testing only once daily may result in missing the surge. Here is an example of my OPK's for one cycle:

On Day 14 of my cycle, I tested at 11:30 p.m. The test was negative (the result line is fairly dark, but not as dark as the test line.)

On Day 15, I tested at 10:00 a.m., only 10.5 hours after my previous test. By this time, the test was positive, and my LH surge had been detected.

Again that same day, I tested at 4:30 p.m, only 17 hours after the previous day's negative test. This test was positive; I was still surging.

And once again that day, I tested, this time at 8:00 p.m. The test was now negative, indicating my LH surge had ended-- and this was still only 20.5 hours after the previous day's test. Therefore, my entire surge lasted less than 24 hours. If I had not taken the additional tests, but followed the instruction to test "every day around the same time," I would have taken a test later that night and missed my surge altogether.

So, if you are unable to detect your LH surge, try testing twice a day! It is possible that you are not ovulating, of course, but this is not a conclusion you should draw based only on a lack of positive OPK's. If you still have concerns, talk to your doctor.

Incidentally, the length of your LH surge may vary from cycle to cycle. If you visit the OPK Odyssey, you can see pictures of my OPK's from several cycles prior to the one above-- in that case, my surge lasted longer than 24 hours, and I had positive OPK's for two days.

As a footnote, some ovulating women simply just don't get positive OPK's, like some pregnant women don't get positive HPT's (though both scenarios are rare.) The mysteries of the female body! :-)

13. My test line looks "half positive"-- only one side of the line is dark. What does it mean? Most of the time, OPK results are easy to read; the "result" line is one uniform color/darkness. Sometimes, however, you may get a result that looks "half positive," like this:

When this happened to me, I contacted the distributor (in this case, BabyWishes.org)-- I even e-mailed them the above photo. I was told that the darkest part of the "result" line should be compared with the test line, and that this applies to all brands of OPK's.

This month I purchased some Answer brand OPK's, which I had never personally used before. After my LH surge appeared to last 6 days (going by the above rule of thumb), I made the unsettling discovery that my tap water was also ovulating. So I called Answer's 800# and asked the same question. This time I was told that the dark part of the line must be at least 50% of the total width to be considered positive. Going by THAT, the picture above would be considered negative. (And, in retrospect, my LH surge actually lasted a common 2 days-- and my kitchen faucet is not currently fertile.)

So, it appears that my information from BabyWishes was incorrect; it does, in fact, depend on the brand of OPK.

14. How is an OPK different from the Clearblue Fertility Monitor? OPK's measure only one hormone, luteinizing hormone (LH.) They are a yes/no diagnostic device ("qualitative") and will tell you only if your LH is surging (which means ovulation may happen within 12-36 hours.)

The Clearblue Fertility Monitor is a digital device which "reads" test sticks. The test sticks measure LH, but unlike OPK's, also measure estrogen, another girl hormone-- estrogen also rises prior to ovulation, usually a day or two before LH surges. Therefore, the Fertility Monitor ("FM") can detect more subtle changes in your fertility. The digital device reads "Low" (both LH and estrogen are low), "High," (estrogen is increasing, LH is increasing but not yet surging), and "Peak" (LH is surging and estrogen is high.)

While the point of the FM is to allow the device/computer to read the sticks (it has a "memory" and "learns" your cycles), it is possible to read the sticks with the naked eye (for the most part.) With the wick (pee end) on the left, the LH line is on the left, and estrogen on the right. Interestingly, the estrogen line gets lighter when estrogen increases; the LH line gets darker when LH increases.

For comparison's sake, here is a "High" FM stick. LH and estrogen are increasing. The OPK is merely "negative," indicating no LH surge is being detected:

And here is a "Peak" FM stick. LH is surging (dark blue), estrogen is high (light blue.) The OPK is positive:

15. Can I use breastmilk on an OPK? I don't know why you'd want to, but it's my peestickaholic duty to find out for you! So I tried it:

I used milk on the top test, and regulation pee on the bottom test. As you can see, though the properly-used pee test is positive (LH surge detected), the milk test is, to use a technical term, majorly negative. (You can, however, see my fingerprint where I accidentally touched the test window, and the dye pooled around it. You'd think CSI would have featured this phenomenon before.) So, drop those drawers, not the nursing panel on your bra!

16. Can I still use pee that's been sitting in a cup for several hours? LH (like hCG) does break down and leave your urine after awhile, but not that quickly. If you need to save your pee for a later time (for whatever reason!) you can collect it and use it later. (I don't know exactly how fast LH breaks down, but hCG has a half-life of 24 hours, meaning the total amount will be cut in half for every day it sits out. Since LH and hCG are extremely similar, I would imagine the half-life of LH would be approximately that.)

I experimented with this. At 7 p.m. I had a positive OPK. I left the urine in my Pee Catcher in my bathroom overnight and dipped another OPK in it the next day at 4 p.m. (21 hours later.)

The OPK on top is the original positive using fresh pee. The bottom test used that same pee 21 hours later. It's clearly positive (this photo was taken when the top test had dried and the bottom test was still wet, hence the slight color variation.) While I wouldn't recommend keeping your pee around for days (if you have less LH during your surge than I do, it may dissipate from your urine faster than it does from mine), I would also not be concerned about using pee a few hours old. Storing it in the refrigerator will slow the breakdown and keep the hormone around longer, but even I have my limits.

17. Are Persona and Fertility Monitor sticks interchangeable? The Persona is an electronic fertility device sold only in Europe and marketed as a contraceptive. The Clearblue Fertility Monitor is an electronic device sold in North America and marketed as an aid-to-conception. While the devices look different on the outside, they both work by reading peed-upon sticks, and both sets of sticks detect luteinizing hormone (LH) and estrogen. Furthermore, both devices (and sticks) are manufactured by Unipath Ltd.

Officially, I doubt the company will admit to it, but I do believe the sticks are interchangeable. I base this upon my experiments with Persona sticks (thanks to my Irish friend!) and several people who have contacted me, informing me that they have successfully interchanged sticks (using FM sticks in the Persona, and Persona sticks in the FM), most of whom were ex-patriate Persona owners who found it cost-prohibitive to have Persona sticks shipped from abroad and used (locally-obtained) FM sticks instead.

VERY IMPORTANT: while the STICKS are interchangeable, the MONITORS THEMSELVES are not. The computers inside rely on different algorithms for determining two different things. Remember, the "best time to get pregnant" is NOT the same as "the only time to get pregnant." When the Clearblue says you are "more fertile," it does not mean you are "not fertile" the rest of the time. Similarly, while the Persona says you are "borderline fertile," it doesn't mean you are "likely to get pregnant." When trying to avoid pregnancy, "possibly fertile" means "avoid like the dickens," whereas when trying to become pregnant, "possibly fertile" means "not good enough odds."

18. My OPK results don't align with my ovulation pain. Is the OPK wrong? The official medical word for "ovulation pain" is "mittelschmerz," which is the official German name for "I am a jelly donut." Wait, I'm confusing my German phrases. Actually, "mittelschmerz" means, literally "pain in the middle." If you are like me, you grew up hearing "Ow, I'm ovulating" from big sisters or girls at school. Much as I love my sisters, they really didn't know what they were talking about. Who am I kidding? All little sisters love announcing a revelation like that ;)

Most women don't really feel themselves ovulate. ("I do!" you're exclaiming.) Probably not. ("But look at my chart! It only happens around ovulation!") Yup, happens to me too . . . and it may be occurring the exact moment of ovulation. But in fact, studies on mittelschmerz have shown that a woman is just as likely to have these pains days before ovulation (when the egg follicle is growing, or a build-up of mucus in the Fallopian tubes getting ready for ovulation) or after ovulation (the egg bursts out of its follicle with some force-- sometimes women will experience spotting or moderate bleeding at this time.) Yes, you may actually feel the egg burst out of its follicle at the moment of ovulation-- but you could just as well be feeling the pre- or post-ovulatory effects. Or that burrito.

Therefore, if your "ovulation pain" doesn't seem to jibe with the timing of your OPK, go with your OPK-- the presence of the hormone in your urine is a much better detector of ovulation than trying to make sense of twinges or tingles in your abdomen.

For what it's worth, feeling or not feeling "ovulation pain"/mittelschmerz isn't important; some women feel it, some don't, some feel it only sometimes, some are in major pain (up to and including emergency room visits suspecting appendicitis), some are "Hmm, I felt a little twinge." All are variations on normal, and don't mean you are more or less fertile or anything like that.

19. Does an OPK have a time limit like an HPT? Kind of. There is a time limit on OPK's (as they are, like HPT's, a "rapid assay diagnostic") but it is not as strict or consistent as the 10-minute across-the-board HPT rule. Read the instructions that came with your OPK's to see the recommended limit for that particular test, as they can be quite different.

Clearblue Easy OPK's say to "discard after 10 minutes." (I have found that this brand will always fade/deteriorate and become unreadable quickly, so make sure you read the results within 10 minutes.)

Answer Daily Ovulation Trackers (dip-strips) say to "discard after 8 minutes," though in my experience the results will not change with time and remain readable for awhile.

Answer Quick & Simple One-Step Ovulation Test (midstream) says "result can be read up to one hour," though again, I've found the results to remain visible for days.

20. Will I see my OPK lines get darker before I get a true positive? Maybe. Some women do experience a "fade-in" pattern, and some experience an "almost positive" shortly before their true positive. However, it's not necessary to observe this pattern. In fact, you might see your test darken and then get lighter. It doesn't necessarily mean you missed your surge; some LH (luteinizing hormone) fluctuation is normal, and there are variations in the individual tests as well (some have more or less dye, for instance.)

Ultimately, there is no need to compare your OPK's; each test can be read in isolation, either positive or negative. If you are one of the women who sees a fade-in pattern, consider yourself lucky; you have some extra, advance notice of your impending LH surge.

21. Does ovulation occur while my test is positive, or will the OPK become negative again first? Ovulation occurs shortly after LH levels peak. However, there is no way to predict whether your OPK will still be showing a positive result during the actual moment of ovulation or whether your OPK will go back to negative first. Remember that it takes time for the hormones in your bloodstream (such as LH) to be metabolized into your urine. By the time your LH surge is reflected in your pee, it has already been peaking in your blood for a short while. Likewise, after your blood levels go down, it takes awhile for your pee levels to decrease.

Because of this "lag time" and the fact that you can't predict how long it will take your body to metabolize LH into and out of your urine, there is no way to know whether your egg follicle actually ruptured while your OPK was positive, or after the OPK became negative again.

22. I'm taking Clomid or Femara to induce ovulation. Will that affect my OPK results? Generally speaking, neither Clomid nor Femara will affect your OPK results; women who take these drugs can continue to use OPK's. However, there may be an issue if you begin using the OPK's too close to the time you take your meds (normally not a problem because the drugs are taken earlier in the cycle than you would use an OPK.) To be sure, ask your doctor, but you will probably be able to use OPK's during medicated cycles.

23. I chart my fertility and my mucus signs don't correspond to my OPK results. Which should I believe? Most women learn to chart their cervical mucus out of a book (such as Taking Charge of Your Fertility by Toni Weschler or The Art of Natural Family Planning by John & Sheila Kippley) or pick up the basics from websites or fertility charting software (like Ovusoft or Fertility Friend.) While many women do learn how to observe mucus adequately this way, some women would benefit from in-person instruction by a certified NFP or FAM teacher. (Yeah, I'm biased ;) It can be difficult for a newbie to interpret her mucus properly without some help!

For example, the term "eggwhite cervical mucus" (known as EWCM) is thrown around to mean "most-fertile mucus." However, strictly speaking, any cervical mucus is potentially fertile (though we generally do distinguish between "less-fertile" and "more-fertile.") Mucus can be tacky or sticky (stretching less than 1/2''), stretchy or "eggwhite" (stretching 1/2'' or more), creamy or lotiony (kind of like Alfredo sauce), gummy or like rubber cement, watery, cloudy or opaque, clear, yellowish or greenish or blood-tinged (pink.) Mucus can be plentiful (enough to require a pantyliner) or scant (observed only once during the day, and not very much.) In other words . . . "EWCM" is just the tip of the iceberg!

Some methods of NFP, namely the Creighton Model ("CrM," a mucus-only method that does not use basal temperature to cross-check fertility signs), have very stringent, objective classifications of mucus, such as "10DL" ("stretchy, damp, and lubricative") or "10KL" ("stretchy, clear, and lubricative.") My CrM-using friends laugh at my silly little "creamy" and "EWCM" terms ;)

So, some women, relying on message board jargon or software abbreviations, may discount what they see if it's not clear with a 3'' stretch (which is the image conjured by the term "EWCM.") In other words-- you may actually have mucus.

If there is a true discordance (i.e. you're confident in your mucus observations and they really don't jibe with your OPK's) in general, go with the OPK's. Ovulation tests measure the hormone in your urine, and can't be affected or disturbed by as many variables as mucus observations can. For instance, taking an antihistamine for allergies can dry up your cervical mucus even when you are ovulating. Or, if you have taken the oral contraceptive pill within the last 12 months, your cervical crypts (responsible for producing mucus) may be atrophied and produce no, scant, or poor-quality mucus. (The hormones in the Pill cause the crypts to shrivel up; this is reversible and they will heal with time, but it can take up to a year for them to return to normal.) And that's just a couple of examples.

24. My question isn't answered above. Can I ask you? If you have a question that you think should be included in the FAQ above, please feel free to send it to me! I may include it in the FAQ above, even if I do not respond directly. Please realize that I am not a medical professional and cannot advise on medical issues.

If you have questions or comments about something on the site, feel free to contact me as well. I am thrilled that my little old pee site has become so popular, but that also means I simply don't have the ability to respond to every e-mail. Thanks for loving me anyway ;)

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