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What do ovulation tests measure?

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 confirm successful ovulation at home.

Written on 6/25/21

what do ovulation tests measure

Ovulation tests allow you to time intercourse around when you’re most fertile in order to conceive.

Many women have used ovulation tests when trying to conceive. These helpful tools allow you to time intercourse around when you’re most fertile in order to conceive.

While this information is really important, have you ever wondered exactly what ovulation tests measure? Let’s dive in!

What are ovulation tests?

Ovulation tests are hormone tests that help you identify your fertile window. They come in several different forms and can also show results differently.

Some tests are strip-based, while others come in plastic casing. Many ovulation tests are threshold-based, meaning they turn positive when a certain amount of hormone is detected in urine. Other ovulation tests are semi-quantitative, which means the intensity of the line can show exactly how much of the hormone is present in urine.

If you’re not sure which ovulation test is right for you, check out our founder Amy’s Epic Ovulation Predictor Kit Experiment! She tested the most popular ovulation test brands and summarized her findings to help you make an informed decision.

What do ovulation tests measure?

Ovulation tests measure luteinizing hormone (LH) levels in urine. LH is one of the hormones that can help predict your fertile window.

At the beginning of the cycle, your brain releases follicle stimulating hormone (FSH), which signals to the undeveloped eggs in your ovaries that they need to start maturing. As these follicles grow and mature, they start producing estrogen. Once a dominant follicle is mature and estrogen reaches a certain level, it sends a signal to your brain that the dominant follicle is ready to ovulate.

This signal triggers a surge in LH, which tells your ovaries it’s time to release a mature egg. The surge causes the follicle to rupture and ovulation typically occurs 24-36 hours after an LH surge.

When you use ovulation tests, you can detect this increase in LH and then time intercourse around ovulation accordingly, so that you maximize your chances of getting pregnant. A positive ovulation test — like Proov Predict — indicates that LH is surging and you’re entering the two most fertile days of your cycle.

It’s important to note that some ovulation tests measure LH and estrogen in urine. These tests attempt to detect a rise in estrogen in order to predict a longer fertile window. If you’re curious about which hormones your specific ovulation test measures, you can typically find this information on the box or in the instructions. 

Why should I use ovulation tests?

Having sex during your fertile window is essential if you want to get pregnant. In fact, studies show that failure to conceive is mainly caused by mistiming of intercourse in healthy couples.

Contrary to what we’re taught in sex education, there are only a few days each cycle when it’s possible conceive. These days occur around ovulation — after all, without an egg there is no chance at pregnancy!

A recent study on 330 women trying to conceive found that only 13 of them were able to accurately estimate their ovulation day and only 27% of them accurately estimated it occurred on the days of peak fertility (i.e. your fertile window). The women who were able to identify their fertile window used — you guessed it! — ovulation prediction methods like ovulation tests.

Timing intercourse is a critical piece of the pregnancy puzzle because an egg can only survive for about 12-24 hours after ovulation. The good news is healthy sperm may live up to 5 days in your reproductive tract. So, having intercourse a few days before ovulation actually occurs can help optimize your chances at getting pregnant.

In fact, studies show that waiting until after ovulation to have intercourse considerably decreases your chances of conception. Your chances of conception the day before ovulation is about 41%, while your chances the day after ovulation drop to only 8%.

Even if you’re not actively trying to conceive, ensuring you’re ovulating can give you insight into your overall health. Lack of ovulation (also called anovulation) may be a sign of a greater health issue.

The most common cause of anovulation in women of childbearing age is by far Polycystic Ovarian Syndrome (PCOS), a frequent yet highly under-diagnosed endocrine disorder which affects up to 12% of women. PCOS is also one of the main causes of infertility.

Note that anovulation may have other causes too, including:

  • Extreme stress (psychological or physical)
  • Perimenopause
  • Anorexia
  • Obesity
  • Thyroid disorders
  • Primary Ovarian Failure

This being said, an anovulatory cycle may happen from time to time in healthy women with regular cycles. Sporadic anovulation is generally normal, however if it becomes a pattern cycle-to-cycle, we recommend consulting your doctor.

When do I use ovulation tests?

Since ovulation tests are meant to predict ovulation, you’ll ideally want to start using them early on in your cycle. Ovulation typically occurs midway through your cycle.

While many women are taught ovulation occurs exactly on cycle day 14, this isn’t always necessarily true. Cycles can vary drastically in length — a normal cycle may last anywhere from 21 to 35 days. If your cycle is exactly 28 days long, ovulation is likely to occur on cycle day 14 but the day of ovulation varies depending on cycle length.

This is why we recommend taking into account the usual length of your cycle when determining when to begin using ovulation tests. If you are using Proov Predict, we recommend beginning testing 18 days before your next suspected period. So if your cycle is 28 days long, you’ll want to start testing on cycle day 10. (Don’t worry, our LH tests include a handy chart to help you out with the math!)

Earlier in your cycle we recommend testing once per day in the morning. Since LH surges in blood anytime between midnight and 8 am, and it takes a while for it to pass in urine, you may want to test using second morning urine.

However, LH surges can be short and easy to miss. Because of this, we recommend testing twice per day as you approach peak fertility — once in the morning and once in the evening — to ensure you’re able to catch the surge.

Once you get a positive ovulation test, ovulation usually occurs about 12 to 36 hours later. This is the optimal time to have intercourse if you’re TTC!

what do ovulation tests measure

If you are using Proov Predict, we recommend beginning testing 18 days before your next suspected period.

Do ovulation tests confirm ovulation?

Though the name may be deceiving, ovulation tests do not actually confirm whether or not ovulation occurred. As we mentioned, ovulation tests measure LH in order to predict ovulation; you need an entirely different tool to confirm it!

Enter PdG tests! Proov PdG tests are the first and only FDA cleared PdG tests to confirm successful ovulation at home. Our tests measure PdG, a urine metabolite of progesterone, which is only released after ovulation has occurred.

While a single positive PdG test confirms ovulation, we like to see 3-4 positive test results on days 7, 8, 9, and 10 past peak fertility (i.e. a positive LH test) with a positive result on day 10 to confirm successful ovulation. Successful ovulation refers to an ovulatory event in which an egg is released and PdG levels remain elevated for long enough to allow for the best possible chance at conception.

Now that you know what ovulation tests measure, you’re equipped with powerful information to help you along your trying to conceive journey! We’re always here to support you.

Have questions? Email us!