The black color of menstruation may be caused by physiological factors, endocrine hormone disorders, organic lesions and other reasons. 1. Physiological factors: when affected by cold and emotional stimulation, the hormone secretion in the body will fluctuate, and the menstrual blood may temporarily appear black, at this time, there is no need to worry too much, and you can adjust your habits. 2. Endocrine hormone disorders: when the hormone level in the body is disordered, estrogen is insufficient to make the endometrium proliferate, and progesterone is insufficient to make the blood vessels in the uterus become thicker, which will lead to low menstrual flow and blackish menstrual blood. 3. Organic lesions: If there are polyps, fibroids, inflammation and other factors in the uterus, it may also cause the shedding of the endometrium to be unsuccessful, leading to changes in the color of menstruation. There may be other reasons for the black color of menstruation. It is recommended to go to the hospital in time, complete the examination to clarify the cause of the disease, and then give targeted treatment or therapy under the guidance of the doctor.