If the menstrual period is dark at the beginning, the main reason is that the menstrual blood is not discharged properly, and the peeled endometrium stays inside the uterine cavity for a long time and becomes darker when it flows out from the vagina. The color of menstruation itself is dark red, and in addition to blood, there is also cervical mucus, endometrial debris, and vaginal epithelial cells. If you eat cold food, get cold in the abdomen, or get depressed during this period, it may cause blood vessels to spasm to varying degrees, and your period may become lighter and darker, even accompanied by blood clots and abdominal pain. Depending on the situation, you can drink more warm water or keep your abdomen warm and observe if the color turns dark red after the menstrual flow increases. Some endometrium inflammation and local tissue edema may also be accompanied by abnormal color of menstrual blood on the first or last day of menstruation. If necessary, do gynecological examination and take oral anti-inflammatory drugs under the physician’s instruction.