Normal menstrual blood is bright red or light red, menstrual blood is black in the following cases: 1, gynecological inflammation. In addition to blood, menstrual blood is also mixed with the shedding of the uterine lining, epithelial cells, etc. When there is gynecological inflammation, menstrual blood is black.2. Weakness of qi and blood. If you are weak in qi and blood, the blood will be stagnant, and if it is stagnant, it will not pass, and if it does not pass, the menstrual blood will be black.3. Cold evil enters the body. When women suffer from cold and consume too much cold food, the menstrual period may appear black and small amount.4. If the menstrual blood stays in the body for too long and the amount of menstrual period is small, the menstrual blood will be black. Pay attention to keep warm, drink more hot water, don’t eat cold food, soak your feet in hot water, and pay attention to hygiene during menstruation.