Understanding a Positive Ovulation Test

If you use or plan to use ovulation tests to determine when you’re ovulating, you need to make sure you have a proper test, know how to use it, and know how to read the result. 

This post will address common questions that women have about ovulation tests.

What is an ovulation test?

An ovulation test detects the level of luteinizing hormone (LH) in your urine. Approximately 12 to 36 hours (48 hours in some women) before ovulation occurs, there will be a surge in LH.

This LH surge stimulates the ovaries and causes the rupture of follicles and subsequently, release of an ovum in a process known as ovulation.

By testing your urine daily, at more or less the same time, you can successfully detect the LH surge. In some cases, you might need to test twice to help you detect the surge.


It can be hard to plan pregnancy when you’re unsure of your fertile window. This is especially true in women who have irregular cycles due to polycystic ovary syndrome (PCOS), thyroid disease, or endometriosis. Check out what you need to know to find the best ovulation test here.

When should you test for ovulation during your cycle?

This depends on the test you use. For some standard ovulation predictor kits (OPKs), you should have an idea of your cycle lengths before starting to test.

Some brands such as TrueStick recommend that you start testing on day 11 of your cycle if you’re unsure of your cycle lengths. If the test kit does not come with a chart, you can use an online ovulation calculator to track your cycles so that you know when to start testing.

Other tools such as the Clearblue ovulation predictor kit measure hormonal changes from your baseline measurement. But you have to start using the kit before your LH surge, so it is important that you read the instructions in the pack to know when to test.

Do not start testing later in the cycle just to save up on test sticks—by missing infertile days, you could also fail to pinpoint your fertile days.

Cheaper ovulation tests like Wondfos require an absolute concentration of LH in urine, so there’s no need to start testing early. This test can establish any baseline. So, relax and know you do not have to force yourself to test right before the surge starts.

One drawback of the Wondfo ovulation test is that you might miss the surge if the hormone levels in your urine are too low.

At what time of the day should you test and what is the best way of testing?

First morning urine testing is not recommended for ovulation kits because you run a high risk of missing your LH. When the surge occurs, your LH levels will still be too low in your urine for the test to detect the hormone. The surge could even end by next morning when you take another test.

The best test time to test is 2 p.m., but it is also fine to test between afternoon and 8 p.m. Many brands recommend that you test in the afternoon. This is because you typically have your LH surge in the morning, and the hormone can take several hours to be detected in your urine. 

For best practice, however, you should always read the instructions of the manufacturer before testing. 

Try to take the test at the same time every day, best during afternoon hours. Do not drink too much fluid prior to testing and refrain from urinating at least 4 hours before the test.

This video from Clearblue shows you how to use the Clearblue Advanced Digital Ovulation test.

What can a positive ovulation test tell you?

An OPK indicates whether your egg (or ovum) will be released from your ovary. Your pituitary gland releases LH right before ovulation starts, and ovulation tests detect exactly that.

The detection of an LH surge is indicates a positive result. After getting a positive OPK test result, this implies that you will possibly ovulate in the next 24-36 hours, and this time span is ideal for intercourse if you’re trying to conceive.

If the test is positive, what should you do next?

It is advisable is to have intercourse during the window of 12–24 hours right after a positive result. The chances of fertilization to occur are much higher when semen is inside the vagina prior to ovulation than on the precise time and day of the ovulation.

If positive, how soon after the test will you ovulate?

In most cases, you will ovulate one day after getting a positive ovulation test result. Sometimes, you will ovulate on the day you get a positive ovulation test.

Of course, it would be impossible to test every hour, so the LH surge can be complex to pinpoint. The majority of women ovulate 12–48 hours after the initial LH surge, and if you get a positive result, you will need to have intercourse as soon as possible.

Is a positive test a clear sign of ovulation?

Probably, but this is not necessarily the case. An OPK can detect that your body is preparing to ovulate, but a positive test is not a 100% sign that a mature egg will be released from one of your ovaries.

Women who have hypothalamic amenorrhea, polycystic ovary syndrome (PCOS), or irregular cycles should be aware that a positive ovulation test DOES NOT confirm that ovulation will occur.

If you have any of the above mentioned hormonal disorders, you need to test for the whole month. But even in these cases, results will not always be 100% sure. You might be better off using other fertility tracking aids such as OvaCue.

Can you have a false positive ovulation test?

In 9 out of 10 cases, a positive result is accurate. The utmost certain and 100% sure way to verify ovulation is with an ultrasound at a gynecologist’s office.

Bear in mind that fertility medicines like Clomid (clomiphene) can give you a false positive (especially when you test early during your cycle).

Further, medications like Danazol, human chorionic gonadotropin (hCG) injections, and menotropins affect the test result and give inaccurate results.

How are the results interpreted? Are these interpreted in the same way as pregnancy test results?

Ovulation tests are not to be mistaken with pregnancy (hCG) tests.

A test band of the same or greater color intensity than a control band indicates a positive ovulation test. When the test band is lighter and less intense in color than a control band, or is not very visible, LH levels are not high enough in urine, so the test is negative.

For pregnancy tests, on the other hand, you need to look at the test line only (without focusing too much on intensity). 

To help you interpret your OPK test results, consider the following:

  • Two clear lines are a true positive
  • Just one control line is a clear negative
  • A control line and light (faint) test line is also a negative

A pregnancy test with a lighter or fainter test line could signal a positive result, but with an ovulation test, this is considered negative. If the control line is not clearly seen, the ovulation test is invalid and has to be repeated again.

The video below demonstrates OPK test line progression.

Further Reading

  1. Lobmaier JS, Bachofner LM. Timing is crucial: Some critical thoughts on using LH tests to determine women’s current fertility. Horm Behav. 2018 Jul 20. pii: S0018-506X(18)30166-1. doi: 10.1016/j.yhbeh.2018.07.005.
  2. Manders M, McLindon L, Schulze B, Beckmann MM, Kremer JA, Farquhar C. Timed intercourse for couples trying to conceive. Cochrane Database Syst Rev. 2015 Mar 17;(3):CD011345. doi: 10.1002/14651858.CD011345.pub2.
  3. Eze CU, Ugwu HC, Eze CU, Ochie K, Nwadike IU, Otika C. Prediction of Normal Ovulation by Sonographic Folliculometry Involving Natural Cycles among Women in Ojo, Southwest Nigeria. West Indian Med J. 2015 May 13;65(1):134-140. doi: 10.7727/wimj.2014.103.
  4. Crews BO, Moley KH, Gronowski AM. False-positive results in home ovulation prediction devices due to very low concentrations of human chorionic gonadotropin. Clin Biochem. 2013 Oct;46(15):1625. doi: 10.1016/j.clinbiochem.2013.07.017.

I’m Princila, founder of Check Ovulation and a proud mom of two. I’m an alumna of James Lind Institute. After working in clinical jobs, my passion for writing took its toll, and I ended up switching careers to work in the medical publishing industry. I also have a passion for healthy food, which prompted me to take several online courses in nutrition and health offered by Wageningen University. (I still haven’t completed the courses thanks to my busy mommy schedule!). When I’m not writing/editing scientific and medical manuscripts or taking care of my family, I use my free time to research, learn, and write about healthy living. I have also authored a few books in the self-help niche using the pen names Princila Murrell or PN Murray.

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