The ClinicalGuard LH Urine Ovulation Test is a fast-acting ovulation test. It works by detecting the presence of Luteinizing Hormone ("LH") in urine. LH increases dramatically just before ovulation - a woman' most fertile time of the month to conceive. The increase in LH also known as LH-Surge - is the hormonal change that precipitates ovulation (the release of the egg). The ClinicalGuard test takes just a few seconds to collect your urine, and five minutes to obtain results. Note: The color intensity of the test bands on the test vary depending on the concentration of LH hormone detected.