Menstruation is a barometer reflecting the health of the female reproductive system, normal menstruation is dark red non-clotting blood, found menstrual blood is black clots what is going on? If you eat too cold food before or during menstruation, or if your body is stimulated by cold, it will affect the discharge of menstrual blood and cause it to clot in the uterine cavity. 3. This phenomenon may be caused by women not paying attention to their own maintenance before and after menstruation, eating too spicy and stimulating food, excessive emotional changes, and excessive physical fatigue.