The causes of excessive menstrual bleeding in women are more: 1. Endometritis. Usually the endometrium is thickened, which can lead to excessive menstrual flow. 2. Uterine fibroids. Especially subplasma fibroids can lead to excessive menstrual flow and prolonged menstrual bleeding. 3. Excessive secretion of estrogen in the body. The increased level of estrogen secretion will lead to thickening of the endometrium, which will lead to excessive menstrual blood during menstruation. 4. If a woman is taking anticoagulants, she will also have more menstrual blood. 5. Women suffer from blood disorders. For example, leukemia, aplastic anemia, etc., the coagulation system in the body will be dysregulated and coagulation dysfunction will occur, leading to long menstrual bleeding and increased menstrual volume. So when women have abnormally increased menstrual flow, they should seek medical attention in time to avoid the phenomenon of anemia.