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Ovulation tests vs. pregnancy tests: Seven differences you should know

Ovulation tests may look similar to pregnancy tests, but they serve a different purpose. They also can’t be used interchangeably because they detect the presence of different hormones. But both are important and empowering tools for managing your reproductive health.

If you’re ready to get pregnant, ovulation tests can provide key insights into your fertile window and help you calculate the optimal time to have sex. Here are seven things you should know.

1. Ovulation tests measure a different hormone than pregnancy tests.

So, what do ovulation tests measure, exactly? Ovulation tests detect the presence of LH (luteinizing hormone) or both LH and estrogen, depending on the type of ovulation test you buy. Home pregnancy tests, in contrast, detect hCG (human Chorionic Gonadotropin). Both ovulation and pregnancy tests detect hormones in urine.

The Clearblue® Advanced Digital Ovulation Test detects both LH (luteinizing hormone) and estrogen.1

2. Ovulation tests have their own nickname.

It’s “OPK,” which stands for “Ovulation Predictor Kit” and is a common acronym people use to refer to ovulation tests. (If you run across the acronym “HPT,” it likely stands for “Home Pregnancy Test.”)

3. Timing matters when taking an ovulation test.

How do you know when to take an ovulation test? Similar to pregnancy tests, it’s important to track your menstrual cycle to determine when to start using your ovulation tests. Once you’ve worked out your cycle length, use the instruction that come with your test to find out when to start testing (you can find the Clearblue® Advanced Digital Ovulation Test instruction leaflet online here).

4. The time of day you take an ovulation test matters, too!

Like many home pregnancy tests, when using a Clearblue® Advanced Digital Ovulation Test, it’s best to use your first morning urine. You can use a Clearblue® Digital Ovulation Test at any time of day, so long as you test at the same time every day.

5. You have a limited window within which to view your ovulation test results.

For instance, when using a Clearblue® Advanced Digital Ovulation Test, low fertility (a clear circle) and high fertility (a flashing smiley face) will be displayed for 8 minutes after it first appears. Peak fertility (a static smiley face) will be displayed for 48 hours.

6. If you have a negative ovulation test, you should test again.

One of the first differences you’ll probably notice between home pregnancy tests and home ovulation tests is their design. While pregnancy tests often include just one or two tests in each box, many home ovulation tests will include enough supplies to test your fertility for several days with a single kit. The Clearblue® Advanced Digital Ovulation Test, for example, includes a test holder designed to be reused with 10 test sticks to help you detect high and peak fertility days. Test daily using first morning urine until you see high fertility (flashing smiley face). Then keep testing (you don’t need to use your first morning urine now – you can test anytime) until you see peak fertility (non-flashing smiley face). Then you can stop!

7. LH surge isn’t connected to pregnancy.

Does an LH surge stay high if you’re pregnant? No. LH peaks during ovulation, and then decreases, whether or not implantation occurs.

When you’re trying to conceive, knowing if and when you ovulate is important. That’s why Clearblue® developed the world’s first one-step ovulation test in 1989 and, 10 years later, launched the world’s first dual-hormone fertility monitor to indicate both high and peak fertile days of the cycle, providing women with more opportunities to get pregnant. The Clearblue® Advanced Digital Ovulation Test is designed to do what all Clearblue® products do: empower you by delivering accurate results.



  1. The sensitivity of the LH detection in Clearblue® Advanced Digital Ovulation Test is 40IU/ml measured against the Third International Standard for urinary LH and FSH for Bioassay (71/264)