The menstrual period is usually 2-8 days, the average is 3-7 days. The menstrual flow is the amount of bleeding per menstrual cycle, usually 20-80ml, if the vaginal bleeding exceeds 80ml it is excessive. The menstrual cycle is generally defined as the period from the first day of vaginal bleeding of the current menstrual cycle to the first day of vaginal bleeding of the next menstrual cycle, which is every 28 days on average. If it is shorter or longer than 7 days, it is considered a normal menstrual cycle, that is, if the menstrual cycle is shorter than 21 days, it is too short, and if it is longer than 35 days, it is a prolonged menstrual cycle. Any abnormality in the volume, duration or cycle of menstruation requires a visit to the hospital.