There is no optimal time to measure ovulation in the clinic, and measuring in the morning is usually recommended. Ovulation tests measure the level of luteinizing hormone (LH) in the urine, and the circadian pattern has no particular effect on LH. This means that there are no major fluctuations in LH levels between 10am and 8pm, so ovulation tests are more accurate during these times. When measuring ovulation, for those who have regular menstruation, it is recommended to start measuring from the 10th day after the start of menstruation, once a day; when close to the day of ovulation (usually on the 14th day), it can be measured twice a day; when the result is found to be weakly positive, it can be measured once every 4 hours, which makes it easy to judge the highest peak of LH, i.e., the weak-to-strong-then-to-weak peak. The peak usually occurs about 24 hours before ovulation, which can be a good predictor of ovulation.