This condition can be caused by a variety of reasons. First, it is possible that the level of estrogen secreted by the ovarian hypofunction is low, resulting in insufficient endometrial proliferation. And menstruation is due to vaginal bleeding caused by shedding of endometrium, so when the proliferated endometrium is less, the bleeding volume will be less, and the low volume is coffee-colored when the discharge is not smooth. If you have already entered perimenopause, you can observe it. If you have not yet entered perimenopause, you should seek medical examination. Secondly, some uterine operations can also cause damage to the endometrium resulting in low menstrual flow, such as uterine evacuation and suction surgery. So you should do a good job of contraception and avoid abortion as much as possible. Third, some endocrine changes can also cause such a situation, such as primary endocrine diseases or hormone level changes caused by indiscriminate use of drugs, emotional changes, overexertion, all these reasons can cause changes in menstruation.