There are several reasons that can lead to low menstrual flow and brown color: First, endocrine disorders, when the body secretes less estrogen, it will make the uterine lining thin, and then the clinical manifestations will make the menstrual flow reduced and brown color. If you want to know the level of hormone secretion, you can choose to go to the hospital and take blood test for hormone six on the 2-4 days of menstruation to know the level; second, ectopic pregnancy, there are a lot of patients with ectopic pregnancy without typical menopausal history, and there will be vaginal bleeding irregularly, the patient will mistakenly think that this bleeding is the onset of menstruation, and this kind of vaginal bleeding will be manifested as low bleeding and brown. The diagnosis of ectopic pregnancy needs to rely on pregnancy test, combined with the results of ultrasonography; third, after the placement of intrauterine device, some patients will experience a decrease in menstrual flow after the IUD, but at this time, the period is usually prolonged; fourth, special circumstances can lead to a decrease in the amount of menstrual flow, such as staying up all night, psychological stress, exams and so on. From the above analysis, we can know that many reasons can cause the menstrual flow to be reduced in brown color.