Normally, menstruation clears in 3-7 days, and it is brown on the 6th or 7th day, and the amount is small. If the menstruation is bright red, it is abnormal for the following reasons: 1. Endocrine disorders. Menstruation is controlled by a variety of hormones in the body. If there is an endocrine disorder, it cannot control menstruation and there is a prolonged period until the sixth day when the blood is still bright red. 2. Inflammation. Genital inflammation can also lead to prolonged periods, slow recovery of the endometrium, and bright red blood at the end of the period period. 3. Organic lesions of the uterus. Commonly there are uterine fibroids, endometrial polyps, etc., which may also lead to heavy menstruation and prolonged menstruation. The abnormal menstruation needs to go to the hospital in time to clarify the cause and then treat the symptoms.