Ovulation prediction kits are helpful for detecting when you're about to ovulate. They measure the luteinizing hormone (LH) in your urine. An LH surge (a high level of LH in your urine) means that you will probably ovulate within the next 24 to 36 hours. You will perform this test in the middle of your cycle.
For example, we recommend you perform this test on days 13 and 15 of your menstrual cycle if you usually get your period every 28 days. Keep in mind, day 1 is the first day of your period. If you do the test every day during your midcycle and do not detect an LH surge, you may not be ovulating.