Ovulation tests work by detecting a surge in the luteinizing hormone (LH) in a woman's urine. This LH surge occurs about 24 to 36 hours before ovulation, which is when an ovary releases an egg. By identifying this hormone peak, ovulation tests help determine the best days for conception. The tests typically involve placing a test stick in the urine stream or dipping it in a urine sample. A positive result indicates that the LH levels have risen to a point that ovulation is likely imminent, showing up as a specific symbol or lines on the test. This helps users know their most fertile window to maximize chances of pregnancy.