There are several reasons for the darkening of menstrual blood as well as the low volume: First, the most common reason is the thinning of the endometrium due to the disruption of women’s hormone levels, which leads to a decrease in menstrual flow. The decrease in endometrial shedding and the weaker contraction of the uterus will result in the blood in the uterine cavity not being able to drain out of the uterine cavity in time, thus leading to the darkening of the blood, mainly through the regulation of hormone levels to improve the symptoms, and if necessary, endometrial biopsy is required. Secondly, it is caused by damage to the endometrium, most commonly due to excessive force of abortion, which damages the endometrium. Again, it is caused by abnormalities of the reproductive system, resulting in the blood in the uterine cavity not being able to drain out of the uterine cavity in time, such as congenital longitudinal uterus or small hymenal orifice, where the blood cannot drain out in time and requires surgical treatment. In Chinese medicine, it is generally considered to be caused by a deficiency of qi and blood, and requires timely qi and blood supplementation.