The causes of menstrual black blood and low volume are as follows: 1. related to thin endometrium, untimely discharge after stripping or the presence of slow pelvic blood circulation, stagnant blood stasis, etc. 2. endometrial polyp ischemia, necrosis, submucosal myoma necrosis leads to longer deposition in the uterine cavity, which also results in low menstrual volume and black menstrual blood. 3. may be related to female endocrine disorders. 4. related to uterine cold. Therefore, women should take proper rest during menstruation, eat more hot food, and drink more brown sugar water or motherwort granules or Gui Zhi Fu Ling capsules to promote blood circulation in the pelvis and accelerate the contraction of the uterus. If the symptoms are not relieved, women should go to the hospital for gynecological ultrasound and sex hormone examination, and take appropriate treatment according to the cause.