The menstrual cycle is usually 21 to 35 days, with an average of 28 days. Therefore, one menstrual period in 20 days belongs to frequent menstruation, which is abnormal.There are several cases of menstruation in 20 days, such as endocrine disorders, abnormal uterine bleeding, mental stress, staying up all night, drinking alcohol and so on. 1. Endocrine disorders: If a woman’s menstrual cycle is usually irregular, only once a menstrual period occurs frequently, may be related to changes in lifestyle, mood changes, etc.; or luteinizing body insufficiency is caused by the need to check the hormone six, you can take oral short-acting contraceptives or progesterone to regulate the menstrual cycle, and the use of medication should be in accordance with the doctor’s instructions. 2. Abnormal uterine bleeding: Menstruation once every 20 days may also be caused by abnormal uterine bleeding, and ultrasound is needed to determine the situation of the cervix to avoid missed diagnosis. 3. Bad habits such as mental stress, staying up late and drinking alcohol can also cause irregular menstruation. In clinical practice, when menstruation occurs once every 20 days, it is necessary to actively consult the doctor to clarify the cause of the disease and then carry out targeted treatment.