Menstruation fifteen days early may be related to menstrual disorders, uterine fibroids, oral emergency contraceptive pills, pregnancy and other conditions. 1. Menstrual disorders: If the patient has recently experienced increased stress and emotional fluctuations, and her menstruation is fifteen days early, it may be due to menstrual disorders, which are mainly caused by abnormalities in the hypothalamus axis. 2. Uterine fibroids: If the patient’s menstruation is fifteen days early, it may be uterine fibroids. The most common manifestations of uterine fibroids are prolonged menstrual period, shortened menstrual cycle, and increased menstrual flow. 3. Oral emergency contraceptive pills: If the patient has a recent history of oral emergency contraceptive pills and her period is fifteen days early, it may be due to irregular stripping of the endometrium caused by hormonal stimulation. 4. Pregnancy-related: If the patient has regular menstruation and a recent history of sexual intercourse, and if the human chorionic gonadotropin test is positive, pregnancy-related diseases such as preeclampsia may be considered. If the patient’s menstruation is usually regular and occurs fifteen days early, it is recommended to go to the hospital in time to complete the relevant examinations, such as ultrasound, etc., to clarify the cause of the disease and then deal with it in a timely manner.