Low dark brown menstrual flow may be due to physiological reasons, or due to gynecological diseases, endocrine disorders, endometrial damage and other pathological reasons. 1. Physiological reasons: women have low menstrual flow on the first or last day of menstruation. It is normal for menstruation to stay in the body for a long time and become dark brown. 2. Pathological causes: gynecological diseases such as cervical adhesions can cause difficulties in eliminating menstruation, which is manifested by small amount of menstruation and abnormal color. Ovarian function decline, estrogen reduction and other endocrine reasons will also reduce menstrual bleeding and abnormal color. In addition, surgery and repeated abortions may cause damage to the uterine lining, thus affecting the amount and color of menstrual flow. When patients have pathologically low menstrual flow and dark color, they need to consult a doctor in time for treatment.