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Women produce leuteinizing hormone (LH.) We have it in our urine most of the month, but increases significantly (the surge) about 12-36 hours before we ovulate. An OPK detects LH in your urine and gives you a positive result when this surge occurs.
OPK's can be used along with basal temperatures and cervical mucus to help determine your most fertile period of the month. Once you have a positive OPK that does not guarantee that you will ovulate. Sometimes you will have a surge, but not quite enough to ovulate at that time. Your body will gear up for trying again with another LH surge. Remember that even the most regular woman will have an off cycle where ovulation does not occur for a variety of reasons.
2. How do I read an OPK?
OPK's are NOT read like HPT's. An OPK has a "control" line and a "test" line, just like an HPT. Unlike a HPT, if a "test" line is present, that 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 (remember, a lighter line is just picking up the LH that you have in your system no matter what day of the month it is.)
If the test line looks almost the same as the control line, try testing again later that same day to make sure you 'catch' the surge. Some brands results will appear as a half-line, this may be a positive result, depending upon the brand of OPK used. It does take practice to get used to reading OPK's. If the brand you use for a month really does not work well for you, consider switching brands.
3. Can an OPK be positive for for more than one day?
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.
If you have a positive OPK for more than 3 consecutive days, your ovary may just be having trouble releasing the egg. This is normal, but if it seems to happen month to month, see a doctor.
4. Should I keep testing once I get a positive OPK?
Ovulation usually happens 12-36 hours after the surge.
If you don't see other signs of ovulation (CM dries up, BBT rises) within a few days of your first positive OPK, take another OPK to check for a positive result. If you have multiple OPKs in the run of the month, talk to your doctor. Polycystic Ovarian Syndrome may cause a woman to have positive OPKs due to high levels of LH all cycle long, with no ovulation. Your doctor will be able to test for, diagnose and offer treatment options.
5. What CD should I start to use the OPKs?
If you've been taking and charting BBT, you may already know approximately when you ovulate each month. Start using your OPK's a few days before you think you may ovulate. If you do not track BBT, but have a 28 day cycle, start your OPKs on CD 10. For every additional day of your cycle add one day to when you should begin testing. If you go an entire month with no surge detected, try taking the OPKs a couple of days earlier and for a couple of days longer next cycle. A cost-wise investment is to purchase OPK test strips from a reputable seller on the Internet. Often 25 - 50 can be purchased for less than $10 if you shop around!
6. Should I use first morning urine (FMU) to test with OPK's?
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. From 2 PM to 10 PM seems to be prime OPK test time! If you did not detect your surge based on your testing time one month, perhaps try taking your test at another time next month. Remember it is important to test approximately the same time each day.
Note: Clearblue Fertility Monitors require FMU.
7. What if your BBT and OPK disagree?
An OPK may be positive 36 hours prior to actual ovulation, and BBT and/or cervical mucus may not reflect ovulation for a full 3 days after that. That leaves a wide window of ovulation opportunity! (almost 5 days!) As we say, when in doubt, BD! (Baby Dance) If you want to know when to test, go by whatever ovulation signs seemed to happen later in your cycle. (ie: EWCM appearing three days after your positive OPK - assume ovulation the day of the EWCM).
8. I went the whole month with no positive OPK... what happened?
Your LH surge may last less than 24 hours, so testing at the same time each day might have led to your OPK showing up negative. BD!
Also keep in mind, some women simply just don't get positive OPK's when they ovulate, yet they are ovulating! If your periods are fairly regular, it is likely you are ovulating. You might have to switch to an alternative method of tracking ovulation, such as BBT, or tracking CM and cervical position. (See Tips for TTC on the side menu).
9. One side of my OPK is 'positive' am I a 'little bit ovulating?' :)
Depending on the brand of OPK, it might be a positive, or it might not. Internet strips will often state that whatever part of the line is darkest is the test line that should be used to determine +/- If the test line is darker than the control line it is +, no matter the width. Answer brand OPK's, require the line be at least 50% of the total width to be considered positive.
10. Can I save my pee to test later?
You can save your urine in a clean container if you don't have your test strip when you 'need to go.' I would not leave the testing any longer than 12 hours after pee was collected as LH like hCG will begin to break down after a while.
11. I had ovulation pain, now my OPK is saying negative? What the huh?
Ovulation pain or "mittelschmerz," has been shown to be any number of things related to ovulation, or maybe not! A woman may have these pains days before ovulation (growing egg follicle is growing, Fallopian tubes filling with mucous getting ready for ovulation) or after ovulation. If the pain and OPK don't match, go with your OPK.
12. Does an OPK have a time limit like an HPT?
Follow the test instructions. OPK's unlike HPT's may show a DECREASING positive (line gets lighter) so you might look at your test later in the day once it is long dry, and see a lighter line, then think 'NEGATIVE!' ... Wrong!
13. My OPK is light, then dark then next day, then light again, but not positive. Why is it not a nice gradual build to a positive?
Some women will have a nice progressing build to a positive. Some may have no lines then, whammo - positive! Some others will fluctuate day to day up to the day of the positive. Some fluctuation is normal, each individual test may have varying amounts of dye.
14. So the OPK is positive. Will I ovulate now or when it is negative again?
Ovulation occurs up to 36 hours after LH levels peak. It takes time for the LH to be metabolized into your pee. By the time your LH surge is reflected in your pee, it has already been peaking in your blood for a short while.
Because of this delay, there is no way to know whether you ovulated while your OPK was positive, or after once your test shows negative again.
15. Will Clomid or Femara affect my OPK results?
There may be an problem if you begin using the OPKs too close to the time you take your fertility treatments. If you are on these medications, your doctor would be able to advise you when should take your OPK.
16. I have two brands of OPK. The test line on one is darker and positive while the other is not quite positive. What's going on?
OPKs like pregnancy tests do have different levels of sensitivity. Some will detect your surge sooner than the other brand. The other possibility is simply the dye used in one test is darker or more abundant than in the other brand, so when you test you see one test with a darker line than the other. If your OPKs don't seem to 'match' then, as we say when TTC, when in doubt - BD! Assume that you ill ovulate in the next few days.
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