There are very many clinical reasons that cause women to have a low menstrual flow and darkening. The most common ones are as follows: First, if a patient usually has regular menstruation and occasionally has a low menstrual flow with blackening, abnormal vaginal bleeding due to preterm miscarriage or ectopic pregnancy must be excluded. The patient’s abnormal pregnancy can be followed by a small amount of endometrial exfoliation and bleeding, similar to menstruation, due to the relatively low hormone levels. Secondly, if the patient has less and darker color from the onset of menstruation, consider that the patient may have a small developing uterus or malformed uterine development, etc. Ultrasound or other auxiliary diagnosis can be done to confirm the diagnosis. Thirdly, if the patient has a low menstrual flow and black color after a uterine operation such as abortion or uterine evacuation, consider that it is caused by endometrial damage, adhesions or cervical canal adhesions. Fourthly, if the patient has low menstrual volume and blackening during the perimenopause, the key consideration is caused by the decline of ovarian function. Fifthly, if the patient has reduced menstrual flow after stressful work or excessive dieting, it is considered that the gonadal axis is affected.