The dark color of menstruation is the cause of low menstrual flow, due to low bleeding blood can not be discharged in a timely manner, accumulated in the uterine cavity or vagina, over time is oxidized, the color will be dark. Normal menstruation should be within one week from the time it comes to be completely clean, if the menstruation is more than one week before it is clean, the first thing you need to do is to do the ultrasound of the uterine attachment to rule out endometrial polyps and other endometrial lesions. If there is no obvious abnormality in the ultrasound examination and the menstrual cycle is basically regular, this situation is generally considered to be a poor function of the corpus luteum. A small amount of bleeding after menstruation is generally considered atrophy of the corpus luteum, which can be treated by adding 10 days of progesterone to enhance the luteal function half a month before menstruation, and if the medication is effective, it can be insisted on for 3 menstrual cycles to improve the function of the corpus luteum.