An ovulation test, also known as an ovulation predictor test or OPK, is a home test that checks a womans urine to determine when she is most likely to be fertile. The test detects a rise in luteinizing hormone (LH) in the urine, which signals the ovary to release an egg. This at-home test is often used by women to help predict when an egg release is likely, which is when pregnancy is most likely to occur.

Ovulation prediction test kits usually come with five to seven sticks, and you may need to test for several days to detect a surge in LH. To take the test, you will need to urinate on the test stick or place the stick into urine that has been collected into a sterile container. The test stick will turn a certain color or display a positive sign if a surge is detected. A positive result means you should ovulate in the next 24 to 36 hours, but this may not be the case for all women.

Ovulation tests can be bought at most drugstores and pharmacies and do not require a prescription. They are convenient to use and can help you identify your fertile window. However, ovulation kits are not perfect, and false positives or consistent negatives can happen. If you are concerned about your results, contact your healthcare provider to discuss your fertility.