The normal menstruation is dark red, sticky, no clots, the symptoms of black blood during menstruation belong to menstrual disorders, the main reasons are as follows: 1, blood stagnation, weakness, poor menstruation, menstrual blood in the uterine cavity stagnation time, menstruation is dark red or even black. 2, endocrine disorders caused by irregular work and rest, often stay up late, lack of sleep leading to fatigue, immune system, endocrine 3, gynecological disease factors, if suffering from pelvic inflammatory disease, endometritis and other gynecological diseases, can also lead to menstrual blood in the uterus is not regulated, resulting in menstrual blood stagnation, resulting in abnormal menstrual volume, black color. 4, psychological factors, long-term mood depression, depression, anxiety, tension, etc. can lead to endocrine disorders, resulting in 5, excessive dieting, due to insufficient nutritional intake, weakness, poor blood flow, which affects the menstruation, not only will the color black, may also lead to dysmenorrhea, menopause, etc.