The interval between two menstrual periods becomes the menstrual cycle, the normal cycle is 21-35 days, if less than 21 days is a short menstrual cycle belongs to menstrual irregularity. Adolescent women may have this problem due to the unstable level of hormones secreted by the ovaries, which can be left untreated and observed in anticipation. Women of childbearing age often stay up late and eat irregularly due to the pressure of life or work. This will affect the ovarian function, causing hormone level disorders and thus shortening the menstrual cycle, pay attention to regulating psychological pressure and lifestyle habits. Women with endometrial polyps, fibroids, these endometrial lesions can also cause shortening of the menstrual cycle, accompanied by heavy menstrual blood flow, prolonged menstrual period and other problems. Women who also have endometrial cancer, where the shedding of the uterus is not limited by hormone levels, may also experience shortened menstrual cycles.