If you can rule out medication or external stimulation, the most likely cause is functional bleeding caused by hormonal disorders in the body. Women’s menstruation is cyclical and self-limiting, and a normal menstrual period should last 2-8 days, with an average of 3-5 days. If it exceeds 8 days, even if the period is prolonged and drenching, you should rule out whether you have used drugs with blood-activating effects during or before the period, or strenuous physical activities. In addition, if you have used birth control pills or other sex hormone drugs during your period, it may also lead to prolonged menstruation. If prolonged menstruation occurs on a regular basis, it is likely to be due to atrophy of the corpus luteum in the body.