Luteinizing hormone (LH) is always present in human urine. It increases just before a woman's most fertile day of the month. This LH increase triggers ovulation. During ovulation, an egg is released from the ovary. Ovulation will occur after 24-48 hours following a positive test, detecting ovulation in advance is very important.

Determine the usual length of the menstrual cycle over the last few months. Then, refer to the Ovulation Calendar Cycle Chart below to determine on which day of the menstrual cycle to begin testing. Consult a medical professional first and follow the instructions.

The ideal time to test is in the afternoon, not early morning, though testing may safely take place from 10 am to early evening. Reduce your liquid intake for 2 hours before testing.