A 4-day period is generally a normal physiological phenomenon. The duration of each menstrual period is called menstrual period, which usually lasts for 2 to 8 days, with an average of 3 to 5 days. Therefore, 4 days of menstruation is a normal physiological phenomenon. Menstruation less than 2 days or more than 8 days are not normal. If the menstrual period exceeds 8 days, even if the period is prolonged, the possible causes are uterine fibroids, endometriosis, endometrial polyps, etc., which need to be treated promptly by a doctor. During menstruation, the body’s resistance will decline. Women should pay attention to keeping warm and preventing the abdomen from getting cold, and should pay attention to keeping the vulva clean and wash the vulva with warm water every day. At the same time, sanitary napkins and underwear should be changed frequently, and sexual intercourse, bathing and swimming are prohibited.