Black menstrual blood is a phenomenon considered abnormal in women's menstrual cycle. This is a warning sign that women's bodies are experiencing some problems that affect their health. According to Dr. Tran Thi Mai Huong, obstetrician and gynecologist at Vinmec Hai Phong International General Hospital: "Women need to learn more about the phenomenon of black menstrual blood and find a way to overcome this condition, helping the menstrual cycle return to normal."