Ovulation Predictor Kits (OPKs)

One of the ways to increase your chances of conceiving is to use ovulation predictor kits (aka OPKs or ovulation tests).


What do OPKs do?

• OPKs show your luteinizing hormone (LH) surge and typically 12-36 hours later your mature egg is released (ovulation). You always have LH in your system so don't be surprised if you always see two lines on your OPK. When your LH is surging you get a positive OPK. A positive is when the test line is darker or as dark as the control line. (Make sure you double check the instructions on the OPKs though). They are not the same as pregnancy tests. 2 lines of varying color do NOT equal a positive. I can't stress this enough!

When should I test?

• Anytime of day is fine but it is recommended that you don't use first morning urine (FMU). LH typically shows up later in the day so testing in the morning may give a misleading result. Just remember to take your OPKs at the same time everyday. You could miss your surge if you don't. (Or you could just do what I do and test twice a day. I'm a bit obsessive lol).

When do I start using OPKs in my cycle?

• If you have regular cycles it will be easy to figure this one out. (It'll be even easier if you've been charting and know about when you will ovulate). If you have the mythical and much sought after 28 day cycle, you should start testing on CD11 so that you don't miss your surge. This would be 3 days before you expect to ovulate. If you've been charting (and I can't recommend doing so enough) you'll know when you ovulate (if you have regular cycles). You should start taking OPKs about 3-4 days before you typically ovulate and BD when you get a positive. If you don't have regular cycles take your shortest cycle subtract 17 days and the number you get will be the day you start testing. (ex. if your shortest cycle is 50 days, start testing on CD 33 or if your shortest cyle is 32 days, start testing on CD15). 

I've gotten a positive! I will ovulate...right?

• Not always. One of the biggest misconceptions is that if you get a positive OPK, you will ovulate. I am perfect proof of that. I frequently get positive OPKs throughout my cycle and don't release an egg. My body typically attempts to ovulate at least 2-3 times before it will succeed (which makes for VERY long cycles of course). OPKs do not tell you that you ovulated. They will only tell you that your body is trying to. You could have a surge and then for some reason not release the egg. The only ways to confirm ovulation are by testing your progesterone levels (blood draw) or by charting.

Why are my OPKs positive many times throughout my cycle?

• The most common cause of frequent positive OPKs throughout a cycle is Poly Cystic Ovary Syndrome (PCOS). In short, PCOS is an imbalance of the female sex hormones and it causes LH to remain elevated causing positive or near positive OPKs throughout a cycle. If you have extremely long or anovulatory cycles and frequently get positive or near positive OPKs it's something you might want to bring up to your doctor.