The reason for black blood from menstruation may be the following: First, there may be blood stasis in the body, because normal blood is bright red rather than black, when there is blood stagnation in the body this part of the blood color will become heavy or even become black. For women, if the usual deficiency of qi and blood, that is, poor blood circulation, it may lead to blood stagnation in a part of the body, and then with menstruation to this part of the blood to discharge, it can cause the blood is black. Second, there may be infection or ulcers in certain parts of the body, when the body has an infection, a certain inflammation will occur, and inflammation often leads to changes in the permeability of blood vessels, the exuded blood may be stagnant or stay in a certain part. As time goes on the color of this blood will turn black, which can also lead to darkening of menstruation. Third, when a woman is malnourished, such as severe anemia can also lead to heavy menstrual color, which can also become black blood. Fourthly, there may be a tumor in some parts of the woman, such as uterine tumor or ovarian tumor, etc. If ulceration or serious infection occurs, the exudate can also be mixed into the menstruation, thus causing the menstrual blood to be black.