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Tracking Your Cycle

Ovulation Tests: How Tracking Your LH Surge Can Help You Conceive

ovulation tests

Ovulation tests are urine tests that help you track your fertile days. They are also called ovulation predictor kits, OPKs, or LH tests. These tests detect the presence of luteinizing hormone (LH) in your urine, which is a sign that you might be close to ovulating.

Using these tests can help you time intercourse around your fertile window. When you get a positive ovulation test, it’s a sign that you are likely fertile. It’s more reliable than some fertility symptoms like ovulation pain.

Ovulations tests can be useful, but they have a few important limitations:

  1. These tests tell you that your body is trying to ovulate, but they don’t confirm that ovulation occurred. It’s possible to release LH and not go on to ovulate.
  2. They don’t always detect your most fertile days, which may fall before the ovulation test turns positive (more on this below).
  3. Some women find the tests annoying to use, and the results can sometimes be difficult to interpret.

What’s the best ovulation test?

There are a few factors to consider when deciding which ovulation test is right for you:

Hormones tested

Many tests detect the presence of LH only, but there are also combined tests available that detect LH as well as estradiol. The benefit of testing for estradiol is that this hormone can increase 3 – 4 days before ovulation, giving you more advance warning and more time to plan intercourse.

Type of test

  • Standard ovulation tests: This type of test contains a test line and a control line. A positive result is when the test line is as dark or darker than the control line. Some people find these tests difficult to read, but others like the fact that the test line gets darker as hormone levels increase, which can indicate that your LH surge is approaching.
  • Digital tests: These tests display results on a computer screen, which removes some of the uncertainty that can come from judging the darkness of the test line.
  • Advanced digital tests: Advanced digital tests detect the presence of two hormones: LH as well as estradiol. Estradiol increases several days before LH, which provides more advance warning of ovulation.
  • Fertility monitors: These types of tests are designed to be used across many cycles, and take into account information from your past cycles to tell you when to take the test, and predict more fertile days.


Digital tests and fertility monitors are considerably more expensive than paper tests. Depending on how frequently you test and how many cycles you spend trying to conceive, the price for these tests can add up. Some people like the clarity and ease of use of digital tests, while others like the fact that you can use paper tests frequently without worrying about price.

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How and when to take ovulation tests

You should always follow the included instructions about when to take ovulation tests, because there may be slight variations between test brands.

When to take standard ovulation tests

When using standard ovulation tests, begin testing several days before you expect your LH surge to begin. The LH surge usually begins 1-2 days before ovulation, though this can vary from woman to woman. If your cycles are irregular, or you have no idea when you ovulate, you can begin testing a few days after your period ends.

Another trick for knowing the right time to take ovulation tests is to pay attention to your cervical mucus. Your cervical mucus follows a pattern during your menstrual cycle of becoming more slippery and stretchy as you get closer to ovulation. These changes are driven by the hormone estradiol. Increasing levels of estradiol are what triggers the LH surge. When you have fertile cervical mucus, this means estradiol levels are increasing, which indicates that the LH surge should occur soon.

When to take advanced digital ovulation tests and fertility monitors

When using advanced digital ovulation tests or fertility monitors, it’s especially important to follow the instructions carefully. These tests work by establishing a baseline level of estradiol in your system, and then comparing the results in the subsequent days to your baseline levels.

It might be tempting to start testing later in your cycle to save money, as these tests are the most expensive kind. But if you test when your estradiol levels have already increased above baseline, the tests won’t work properly, and you may not get a positive result.

What time of day to take ovulation tests

Does it matter what time of day you take ovulation tests? Many women can test at any time of day, assuming urine is not too dilute (this is why it’s recommended to avoid drinking excessive amounts of liquids and avoid urinating for at least two hours before testing).

It’s often recommended to avoid testing first thing in the morning. The reason for this is that the LH surge typically occurs between midnight and 8am, and may not be apparent in first morning urine. If you have a relatively short LH surge and you only test in the morning, it might be over by the time you test the next morning and you would never see a positive result.

But for many women, the LH surge is long enough that this is not a problem. Since your personal LH pattern tends to be similar from cycle to cycle, if you see a positive result in the morning on one cycle, you can safely assume that you will be able to catch your surge with morning testing only on subsequent cycles.

How long after a positive ovulation test do you ovulate?

Ovulation occurs, on average, 24 hours after the LH surge first begins, though this can vary from woman to woman.

It doesn’t matter how long the LH surge lasts, because it’s the initial surge in LH that triggers ovulation. Ovulation typically occurs the day after your first positive ovulation test.

It’s a good idea to start taking ovulation tests several days before you expect your LH surge to begin. This way, when you get a positive result you can be reasonably certain that you’ve caught the beginning of your surge.

Also keep in mind that there is profound variability in how long after the LH surge ovulation occurs. This means that you might ovulate the day after a positive test, the day of a positive test, several days after … or you might not ovulate that cycle at all.

What’s more, women with long cycles or PCOS may experience multiple LH surges within a single cycle before they successfully ovulate.

Does a faint ovulation test line mean ovulation is coming?

It can be confusing to decipher standard ovulation test results. You should expect to see two lines throughout most of your cycle, because you always have baseline levels of LH in your body. It’s only when the test line is as dark or darker than the control line that you have a positive ovulation test.

The pattern of the line getting darker will vary from woman to woman. You might notice your test line gradually getting darker over the course of a day or two, or you might go from a very faint test line to a blazing positive in the same day.

And remember, a positive ovulation test doesn’t guarantee that you will ovulate—it’s only an indication that your body is gearing up for ovulation. Think of a positive ovulation test like a weather forecast. Just because the weatherman says it’s going to rain tomorrow, doesn’t mean it absolutely will.

How many days are you fertile after an LH surge?

Most women are fertile for 1 – 2 days after the LH surge. Ovulation occurs an average of 24 hours after the LH surge first begins, though this figure varies from woman to woman. Your fertile window includes the 5 days before ovulation, and the day of ovulation itself.

However, the very best days to get pregnant are the 2 – 3 days before ovulation—multiple studies have shown that having sex on these days carries even higher chances of pregnancy than the day of ovulation itself.

This means that if you wait for a positive ovulation test to have intercourse, you might be missing out on some of the most fertile days of your cycle. It’s best to think of the LH surge as the beginning of the end of your fertile window.

Do you always get an LH surge before ovulation?

Yes—the LH surge is necessary for ovulation to occur. However, you can have an LH surge without ever seeing a positive ovulation test.

The length of the LH surge varies considerably from woman to woman. It can be under 12 hours or several days long. If your LH surge is on the shorter side, it might be more difficult to catch it with an ovulation test.

If you suspect this is the case, you might want to try tracking your temperature or using an Ava bracelet to detect the fertile window.

Does LH drop after ovulation?

Eventually, yes. But how long it takes for LH to drop can vary from woman to woman.

If you have a long LH surge, you might have multiple positive test days in a row. You can ovulate any time after the first positive result.

Can an ovulation test detect pregnancy?

An ovulation test shouldn’t be used as a substitute for a pregnancy test because it’s not as accurate. But if you’re pregnant and you take an ovulation test, you might get a positive result.

The reason for this is that LH is molecularly similar to hCG, which is the hormone that pregnancy tests detect. However, there’s really no reason to use an ovulation test as a pregnancy test. If you think you might be pregnant, splurge on a real pregnancy test!

View sources

Onset of the preovulatory luteinizing hormone surge: diurnal timing and critical follicular prerequisites.

Chronological aspects of ultrasonic, hormonal, and other indirect indices of ovulation

Daily fecundability: first results from a new data base.

Timing is crucial: Some critical thoughts on using LH tests to determine women's current fertility

Biological functions of hCG and hCG-related molecules

Lindsay Meisel

Lindsay Meisel is the Head of Content at Ava. She has over a decade of experience writing about science, technology, and health, with a focus on women's health and the menstrual cycle. Her work has been featured on The Fertility Hour, The Birth Hour, The Breakthrough Journal, and The Rumpus.

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