How do most ovulation predictor kits work?

Written by:, PhD, Founder and Inventor of the Proov test — the first and only FDA-cleared test to confirm successful ovulation at home.

Written by: Dr. Amy Beckley, PhD, Founder and Inventor of the Proov test the first and only FDA-cleared test to check for successful ovulation at home.

Written on: 5/20/22

Many people use ovulation predictor kits (OPKs) on their trying to conceive journey. These helpful tests empower you with information about your fertility that can help you get pregnant.

But do you know what exactly an ovulation test strip tells you? Keep reading to learn how most ovulation predictor kits work.

how do most ovulation predictor kits work

Keep reading to learn how most ovulation predictor kits work.

What is an ovulation predictor kit?

Ovulation predictor kits are fertility hormone tests that can help you get pregnant. As their name reveals, ovulation predictor kits predict when ovulation should occur — key information when trying to conceive.

Even if you haven’t heard of an OPK, you may have heard of an ovulation test or LH (luteinizing hormone) test. These are all different names to describe the same thing, so don’t let the subtle differences confuse you!

How do most ovulation predictor kits work?

Most ovulation predictor kits measure the hormone that immediately precedes ovulation, to predict when exactly ovulation should occur. They measure luteinizing hormone (LH), which is the hormone that spikes right before ovulation to trigger the release of the egg.

A spike in LH is often referred to as an LH surge. An ovulation predictor kit turns positive when enough LH is present in urine to indicate that LH is surging.

In most women, LH surges about 12-36 hours before ovulation should occur. So, a positive ovulation test indicates that ovulation should be coming in the next 2 days.

Most ovulation predictor kits only measure LH, meaning they help you identify the two days preceding ovulation. However, some ovulation predictors may measure estrogen as well.

Estrogen rises even before LH does. A rise in estrogen as the body prepares an egg for ovulation is actually what causes LH to surge. Elevated estrogen tells the brain that the ovary is ready to release the egg.

Some ovulation predictor kits will measure both estrogen and LH to predict ovulation even further in advance. Sometimes, an ovulation test which measures both hormones will be able to predict ovulation up to 6 days in advance!

how do most ovulation predictor kits work?

An ovulation predictor kit that measures both estrogen and LH may be able to predict ovulation up to 6 days in advance!

So why is predicting ovulation so important?

At this point, you may be thinking, Cool, I know how ovulation predictor kits work. But why should that matter to me? And that’s a great question!

While we think understanding when you ovulate is key for anyone — after all, healthy ovulation is a sign of overall health — it’s especially important for those trying to conceive. Conception and pregnancy can only occur when sperm meets egg.

When does sperm have the opportunity to fertilize the egg, you ask? When the egg is released during ovulation!

However, an egg can only be fertilized for about 12-24 hours after ovulation which isn’t much time. That’s where ovulation prediction kits become so important!

While eggs can only survive for up to 24 hours, sperm can live in the female reproductive tract for up to 5 days. So, having sperm present and waiting for the egg once it’s released gives the sperm the best chance at fertilizing that egg.

In fact, studies show that conception is most likely to occur in the few days leading up to and day of ovulation. This is when you should be timing intercourse for the best chance of pregnancy.

Ovulation tests that only measure LH provide your 2 most fertile days each cycle (the day before and day of ovulation). Those that measure both estrogen and LH can provide up to 6 fertile days each cycle, giving you even more days to “try.”

Curious about different ovulation predictor kits? Our founder, Amy, tested out plenty and you can see her review of them here!

How can Proov help me predict ovulation?

We’re so glad you asked! We have 2 key fertility hormone tests that can help with ovulation prediction.

Proov Predict measures LH to identify your 2 most fertile days each cycle. Even better, when paired with the Proov Insight app you can see your numeric LH values change as you near peak fertility.

how do most ovulation predictor kits work

Proov Complete, on the other hand, measures 4 key cycle hormones. Two of which are E1G (a urine marker of estrogen) and LH.

Not only can you identify your 2 most fertile days with Proov Complete (like Proov Predict), but you can also identify up to 6 fertile days each cycle with E1G. This helps you have the maximum time to try — and we believe more information is better!

Now that you know how most ovulation predictor kits work, you are set with even more information on your trying to conceive journey. And if you need any additional support, we’ll be here every step of the way. 

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