Fertility Prediction: Do Ovulation Tests Work?

Ovulation test strips – sometimes called ovulation predictor kits or OPKs – are at-home urine tests used to detect ovulation. Many women struggling to conceive turn to ovulation kits to try and predict the optimal time each month that they are fertile.


Ovulation tests work by detecting luteinizing hormone (LH) in the urine, which surges before ovulation. For fertile women these tests can sometimes be beneficial, providing an estimation of when they may be approaching ovulation.


But, because OPKs only measures one potential marker of fertility, the LH surge, they can also be misleading. This may prevent them from being effective, or even helpful, for women facing underlying infertility issues.


In this article, Austin, TX board-certified Internist and renowned Women’s Integrative Health Specialist Dr. Ruthie Harper explains the drawbacks of over-the-counter ovulation tests, discusses other methods of predicting ovulation, and explores the implications of OPKs for women suffering from infertility.


How Ovulation Kits Predict Fertility

In healthy women, once every month a mature egg is released from one of the ovaries and is available to be fertilized. This corresponds to a 12 to 24-hour window when fertility peaks, making it the best time to try and conceive.


But while ovulation occurs in the middle of the menstrual cycle, each woman’s cycle is different. So, the exact timing of ovulation can vary from woman to woman and month to month. Since luteinizing hormone (LH) typically surges right before ovulation, OPK tests are designed to indicate when and if a woman is ovulating.


Drawbacks of Ovulation Kits to Predict Fertility

One of the biggest drawbacks to at-home ovulation predictors is that while the test can estimate the time that ovulation should occur, it cannot determine if ovulation has actually taken place. In some cases of infertility, such as LUFS (luteinized unruptured follicle syndrome), a woman experiences a surge in LH, but an egg is never released. So, even though the OPK is “positive” indicating the surge in LH that occur prior to ovulation has occurred, the women still do not conceive because in reality, she does not ovulate.


Ovulation kits are also not useful in predicting fertility for women suffering from PCOS (Polycystic Ovarian Syndrome). This is because PCOS can cause many spikes in LH levels, even without ovulation, so the ovulation test kit can provide misleading results.


Similarly, women who are experiencing a decline in fertility as they approach menopause may experience increased levels of luteinizing hormone, which can result in the OPK test providing false positive results for ovulation.


Women whose LH surges last less than 10 hours and who only use the ovulation prediction kit once a day may miss their LH surge depending on what time of day they test. Additionally, women with lower levels of luteinizing hormone whose LH surges do not quite reach the OPK’s threshold may also get false negative results even if they indeed do ovulate.


Some women regularly experience mini LH peaks throughout their cycle, before the real LH surge that leads to ovulation. They may receive false positive results and have intercourse earlier than they should – which lowers their chances of pregnancy.


And, women with irregular cycles often will receive invalid ovulation predictions, since the test’s kit covers only 5 to 9 days each month. A woman with a cycle ranging between 24 to 40 days may actually have ovulation during a 16 day range, which is much longer than the kit’s effective range.


Other Causes of Invalid OPK Results

If an ovulation prediction kit is not kept in the proper conditions, for example if it is exposed to heat during delivery or storage, it may no longer be able to predict ovulation accurately.


Ovulation tests also do not predict fertility accurately if a woman is taking any fertility drugs containing FSH, LH or HCG, and/or antibiotics containing tetracycline and/or is undergoing hormone therapy.


Ovulation kit results will usually be invalid if the women is pregnant, postpartum, or breastfeeding.


Better Options for Predicting Fertility

The two ovulation detection devices discussed below are more accurate than common, over the counter at-home ovulation prediction kits.


Clearblue Fertility Monitor

This is a palm-sized electronic device that measures the levels of LH and estrogen in the urine and estimates if the woman is currently in the low, high or peak phase of their menstrual cycle. It can then determine ovulation one to two days before it occurs and notify the woman a number of days before.


However, this test may also be inaccurate at predicting fertility if the woman is in menopause, was recently pregnant, is breastfeeding, is suffering from PCOS, or taking certain drugs including: antibiotics such as tetracyclines; is on hormonal treatments such as Clomiphene citrate; or is on fertility treatments containing hCG or LH.


OvaCure Fertility Monitor

This device is a handheld monitor with an oral and vaginal sensor. It measures changes in the electrolyte levels in the saliva which are affected by estrogen every day, and then displays the trends in a color-coded calendar to identify the Optimal Fertility Day. And, the vaginal sensor detects when the body has switched from producing more estrogen to more progesterone, which indicates that ovulation has occurred.


When combined, the data from the dual sensors can better estimate possible ovulation, even in women with PCOS or irregular cycles, as the results do not depend on LH levels.


However, even these more advanced methods of ovulation prediction still do not provide any information about a woman’s key fertility signs, which are cervical fluid or waking temperature.


Accurate Fertility Prediction – Austin, TX

If you are attempting to conceive, using an at-home ovulation test, or the more advanced ovulation predicting technologies can be useful – but they are neither foolproof nor 100% accurate. Charting your key fertility signs is still one of the most important ways to boost your fertility and maximize your chances of conception!


If you have been trying to conceive without success for more than several months, it is best to consult with a knowledgeable physician who can diagnose any underlying problems, as well as help you track your potential fertility dates with greater accuracy using all of the methods above.


Austin, TX board-certified Internist Dr. Ruthie Harper, MD is an Integrative Medicine Specialist and offers a wide array of diagnostic procedures, along with scientifically developed health protocols, that can help your body be better able to conceive. She is passionate and compassionate in helping to diagnose and resolve infertility issues.


If you are struggling with infertility, we welcome you to contact us at Ruthie Harper, MD Integrative Health in Austin, TX. We understand the frustration and stress of infertility – and we are here to assist you with love, compassion, and the latest diagnostics and integrative medical technologies to support you in having the family you have always wanted.


Fertility Prediction & Treatment

Austin, TX






Ruthie Harper, MD


Ruthie Harper, MD

Dr. Harper founded Ruthie Harper MD, her internationally recognized practice in Austin, Texas, in 1999. Since that time, she has consulted with more than 10,000 patients and offers the latest services and techniques in health and wellness in the medical division of her practice, as well as non-surgical rejuvenation and skincare in the cosmetic portion of her practice. Her ongoing success serving the health and beauty industries is based primarily on her innovative integration of research, nutritional science, advanced functional testing, and advanced aesthetics.