How to use ovulation tests (OPKs)

Ovulation tests, also known as ovulation predictor kits (OPKs), are extremely useful when you are trying to conceive.

Ovulation tests help you find the most fertile days in your cycle, so you can make sure to have intercourse on those days when you’re most likely to get pregnant.


Ovulation tests work by detecting a hormone in your urine called luteinizing hormone (LH). Your body always produces some LH, but approximately 12 to 36 hours before ovulation, the level of LH increases dramatically.

Ovulation tests detect this surge and will give a positive result when the amount of LH in your urine is high.

A positive ovulation test indicates that you’re likely to ovulate within the next 1-3 days, and that it’s time to get busy in bed.


Ovulation kits come in two different formats:

Both types are equally reliable. Strip tests are cheaper, while midstream tests are easier to use.

To use ovulation test strips, you must first collect your urine in a container. Midstream tests can be held directly in your stream of urine while you urinate, but many women find it easier to use a container with midstream tests as well.

How to use ovulation kits

  • Collect a sample of your urine in a clean container
  • Dip the test in the urine, usually for 3-5 seconds (follow the packaging instructions)
  • Wait for 3-5 minutes, then observe the color density of the two lines (bands) or the digital test result (see packaging instructions)

With digital ovulation tests, there’s no need for interpretation. They will give you a yes/no answer to whether your LH is surging and ovulation is close. Consult the packaging instructions to see how a positive test result is indicated.

On traditional tests with a control and a test line, a positive result is indicated by a test line that is as dark as, or darker than, the control line. Unlike pregnancy tests, the mere presence of a test line does not mean the test is positive. The presence of a light test line only indicates that there is some LH in your urine, which is normal throughout your cycle.

If you find it difficult to interpret the results of your ovulation tests, you may find it helpful to look up pictures of other women’s tests. has a great ovulation test image gallery with thousands of images of negative as well as positive tests. You need to create a (free) user account to access the gallery.


Start testing a few days before you think you will ovulate. If you don’t know when to expect ovulation, it is usually recommended to start testing around 9-10 days after the first day of menstrual bleeding (cycle day 1).

If you have short cycles, you may want to start earlier; if you have longer cycles, you may decide to wait a few more days.

You should test at the same time every day. Unlike pregnancy tests, ovulation tests should not be taken with your first morning urine (the exception is the Clearblue Fertility Monitor). This is because most LH is produced early in the day, and will not show up in your urine until later. Testing in the afternoon or evening works well for most women.

Avoid testing shortly after a great intake of liquid, which may dilute your urine sample and give an inaccurate result.

Because you may get positive ovulation tests for more than one day, you should keep testing until you get one or more positive tests followed by a negative test. The first day your test is negative again is the most likely ovulation day.


  • A positive ovulation test is not a guarantee that you will ovulate. The body may prepare for ovulation and produce the LH surge, but finally not release the egg. Measuring your basal body temperature in conjunction with ovulation testing will help confirm that ovulation really happened.
  • It is also a good idea to continue to monitor other fertility signs, such as cervical mucus. Combining information from different sources will help you identify the time of ovulation as precisely as possible.
  • If you get conflicting results from ovulation testing, cervical mucus observation and temperature charting, it’s impossible to tell which result is most correct. Pinpointing ovulation isn’t an exact science. Keep making love at least every other day until you are certain ovulation is over.
  • If you never get positive ovulation tests, consider starting testing earlier in the cycle or continuing longer, in case you ovulate very early or very late in the cycle. You may also try to test twice a day in order to increase your chances of catching the LH surge. Measuring your basal body temperature will help confirm that you actually do ovulate.
  • If you get positive or almost positive ovulation tests all the time, you may suffer from a condition called Polycystic ovary syndrome (PCOS), which may lead to difficulties getting pregnant. If your ovulation tests are always positive, consult your physician.