How Accurate Are Ovulation Tests?

In a perfect world, ovulation predictor kits (OPKs) would infallibly detect ovulation, and having baby-making sex while you're ovulating would inevitably lead to pregnancy. The reality is much more complicated, though.

Read on to learn how these simple tests work, how accurate ovulation tests are, how to use them, and the pros and cons of OPKs.

How Do Ovulation Tests Work?

OPKs can detect a surge in luteinizing hormone (LH) production, which occurs roughly 36 hours before ovulation. By timing intercourse shortly after the LH surge, you can increase your odds of bringing sperm and egg together when conception is most likely to occur.

But take note: While ovulation tests work to detect an LH surge that precedes ovulation, OPKs do not test for ovulation. In other words, they can't confirm whether you have actually ovulated. Occasionally, an egg fails to emerge from its follicle after the LH surge, a condition known as LUFS (luteinized unruptured follicle syndrome).

OPKs also don't indicate whether cervical mucus is conducive to fertilization. The mucus produced by the cervix in the mid-cycle, which you experience as vaginal discharge, must have a certain consistency (clear and elastic, like egg whites) to provide a fertile environment for sperm to swim through. OPKs do not monitor cervical mucus.

How Accurate Are Ovulation Tests?

Ovulation tests are more accurate than other methods of monitoring ovulation. According to the U.S. Food and Drug Administration (FDA), when used correctly, these tests are about 90% effective in detecting an LH surge, which is used as a marker for ovulation.

Although, in most cases, OPKs provide an accurate forecast of your LH surge and subsequent ovulation, they are most effective when used together with other monitoring methods.

Other fertility monitoring methods include:

• Examining your cervical mucus
• Charting your basal body temperature (your lowest, or baseline, temperature) first thing in the morning
• Charting your menstrual cycle
• Using an online ovulation calculator

These methods combined can significantly increase your chances of becoming pregnant.

When Should You Take an Ovulation Test?

Ovulation tests work best when you use them in the middle of your cycle when you would be most likely to ovulate. Note that it helps to have a sense of your typical cycle length, so start keeping track now if you haven't already! Irregular cycles can affect your chances of getting pregnant because it's more difficult to determine the correct timing for baby-making sex.

Most people ovulate 14 days before their next menstrual cycle. So, according to the National Library of Medicine, if you consistently have 28-day cycles, you would want to start testing on day 11 (the 11th day after your last period) to catch the LH surge that occurs in the days preceding ovulation. Fortunately, OPKs come with multiple strips, so you can keep testing each day until you detect an LH surge.

How to Use an Ovulation Test

While each ovulation test brand varies a little, they all basically follow the same steps. Read the package instructions carefully and follow them to the letter. General steps for an accurate ovulation test include:

1. Choosing the right day to begin testing based on your menstrual cycle length
2. Urinating directly onto a test strip or into a cup
3. Placing a test strip in the urine (if you urinated into a cup)
4. Reading the test strip for a positive or negative indication of an LH surge

If a surge is detected, you can time your baby-making sex accordingly. According to the American College of Obstetricians and Gynecologists (ACOG), pregnancy can occur five days preceding ovulation and about a day after. So, your best bet is in the few days following an LH surge. If the test is negative, you can repeat the test the next day.

The Pros of Ovulation Tests

While not foolproof, ovulation tests work to predict a fertile window in most people. From convenience, accuracy, and availability, they have many benefits.

Ovulation tests are convenient

Since you only need to use OPKs in the middle of your cycle, it's a little less work than other methods of tracking ovulation. For example, with charting your basal body temperature (BBT), you must commit to checking your temperature every day before getting out of bed.

Ovulation tests are widely available

You can get OPKs over the counter at drugstores, pharmacies, major supermarkets, and convenience stores without a prescription.

Ovulation tests are easy to use

Ovulation kits work similarly to home pregnancy tests—you simply pee on the test stick, activating a chemical that can detect your LH surge. Many OPKs come as a 10-pack, but some contain 20 or more test sticks.

The Cons of Ovulation Tests

Though there are many benefits to ovulation tests, there are also some downsides.

Some drugs may affect how ovulation tests work

Ovulation tests are less accurate when you use some medications. These include:

• Hormonal birth control
• Hormone replacement therapy
• Some fertility drugs
• Antibiotics with tetracyclines

Ovulation tests are less accurate as you age

Some people in their 40s, especially those in perimenopause, have increased levels of LH in their systems at all times. This can make the tests less reliable.

Ovulation tests aren't cheap

These kits cost between $15 and $50, depending on the brand and number of tests included. How many cycles they last depends on how many you use each cycle.

Key Takeaways

Many people wonder if ovulation test kits work. The good news is that for most people, ovulation test kits are accurate when used correctly. If you're older or taking certain medications, including some fertility drugs, ovulation tests may not be accurate. Otherwise, they can be an excellent way to check for your most fertile time of the month so you can time baby-making sex accordingly.

You can also use other methods to determine fertility, such as online ovulation calculators, like the one below.