Dark red and black menstrual blood is caused by stagnant blood in the body. The causes of stagnant blood in the body include: 1. Often eating cold and cold food or being exposed to rain or washing clothes in cold water, especially during menstruation without paying attention to warmth. 2. If you are emotionally depressed for a long period of time, often angry, and your nerves are suppressed, the stagnation of qi and blood stasis in traditional Chinese medicine, that is, being angry a lot, can also lead to stagnation of blood in your body.3. Women who are physically weak and have a problem of insufficient qi and blood can also have abnormal menstrual blood. Weakness of the body with Qi and blood deficiency problems can also lead to abnormal menstrual blood. To improve the problem of dark red and black menstrual blood, you must pay attention to keep warm, especially during menstruation, eat warm food, don’t eat cold dishes, and don’t eat food just taken out of the refrigerator, and also keep a good mood and keep happy. You can take medicines that activate blood circulation and remove blood stasis to regulate, for example, you can take motherwort granules.