Normally the volume of each menstrual period is around 80-100ml. If the menstrual volume is low and the duration is long, a systematic examination is needed as follows: 1. First, a gynecological ultrasound should be done to assess the thickness of the endometrium and the presence of uterine pathology; 2. If the endometrium is very thin and no other pathology of the uterus exists, and the low menstrual volume and long menstrual duration are considered to be caused by internal diseases; 3. Immune system assessment and endocrine system related diseases should also be considered The most common cause of low menstrual flow is after uterine surgery. Repeated abortions or endometrial polypectomy will significantly affect the menstrual flow. drug factor.