It is normal for a period to clear in four days. Period is the duration of each menstrual period of a woman, usually 2-7 days, mostly 3-5 days. The normal menstrual blood volume for women during menstruation is 30-50ml, less than 20ml is considered as menstrual hypomenorrhea and more than 80ml is considered as menstrual hypomenorrhea. Menstrual blood is usually most abundant on the 2nd-3rd day, dark red, non-coagulable and includes, in addition to blood, endometrial debris, cervical mucus and vaginal epithelial cells. Most women are asymptomatic during menstruation. A few may experience discomfort such as lower abdomen or lumbosacral cramping, breast tenderness, constipation or diarrhea, headache, etc. It usually does not affect daily work, study and life. It is recommended that women eat a light diet during menstruation, avoid cold, spicy and stimulating foods, and also maintain a regular work and rest schedule, avoid strenuous night work and strenuous exercise, and pay attention to menstrual hygiene.