The first day of menstruation is the beginning of the menstrual cycle, and a menstrual cycle lasts until the first day of the next menstrual period. Menstruation is due to cyclic changes in the ovaries, which results in cyclic shedding of the uterine lining and bleeding. Menstrual blood tends to be dark red in color, with blood, endometrial debris, and vaginal epithelial cells as its main components. Regular menstruation represents the maturity of a woman’s reproductive function. In general, the menstrual cycle usually lasts from 21 to 35 days, with an average of 28 days. Menstrual period refers to the duration of each menstrual period. In general, a woman’s menstrual period lasts about 2 to 8 days, with an average of 4 to 6 days. The volume of each menstrual period is about 20~60ml. Menstruating women usually have no special symptoms, while some patients may have symptoms of dysmenorrhea or gastrointestinal disorders. If the menstrual cycle is abnormal, it is recommended to go to the regular hospital in time and consult the doctor under the guidance of the doctor.