At 51 years old, two periods a month may be normal, such as ovulation bleeding, or abnormal, which may be caused by menstrual irregularities, uterine fibroids, endometrial polyps and other reasons. 1. Ovulation bleeding: 51 years old twice a month menstruation may be caused by ovulation bleeding, with a transient decline in estrogen levels in the body after ovulation, endometrial stripping related to the amount of bleeding is relatively small, usually physiological phenomenon. 2. Irregular menstruation: At the age of 51, during menopause, ovarian function will gradually decline, follicles will gradually shrink, no longer develop mature follicles, and not be able to ovulate, and fluctuations in estrogen levels will lead to irregular menstruation, with abnormal menstrual flow and menstrual cycle, manifesting twice a month menstruation. 3. Uterine fibroids: 51-year-old women suffer from large myometrial fibroids that invade the uterine cavity or submucosal fibroids, which can affect the normal contraction of the uterus, leading to prolonged menstrual periods or increased menstrual flow. 4. Endometrial polyps: endometrial polyps affect the normal exfoliation and repair of the uterine lining, endometrial polyps may lead to excessive menstrual flow and prolonged menstrual period. There are many reasons for frequent menstruation at the age of 51, so it is recommended that you go to the hospital in time to get a clear picture of the cause of the problem and follow the doctor’s instructions for treatment.