Menstruation refers to menstruation, and the dark color of menstrual blood is considered to be related to anatomical factors, exposure to cold, endocrine disorders and other factors. 1. Anatomical factors: some women’s uterus is overly flexed or the cervical opening is too small, resulting in poor discharge of menstrual blood, which accumulates in the uterine cavity and causes the dark color of menstrual blood. 2. Exposure to cold: If women drink cold or wear too thin clothes before or during menstruation, it will affect the smooth discharge of menstrual blood, and some women will have obvious abdominal pain and dark-colored menstrual blood. 3. Endocrine disorders: for some patients with high mental stress or gynecological endocrine diseases such as ovulation disorders, due to the endometrium is not completely stripped, some patients’ menstrual flow will be significantly reduced, and the color of the menstrual period may also be black. For women with dark-colored menstrual periods, it is recommended to go to a regular hospital to improve the sex hormones, ultrasound and other related examinations, to clarify the cause of the disease and then under the guidance of the doctor to actively treat.