Menstruation every two months is normal with regularity and considered abnormal with irregularity. The normal menstrual cycle is 21-35 days, but each woman’s physical condition is different, and the duration of the menstrual cycle is also different. Menstruation is mainly affected by the hypothalamus-pituitary-ovarian fertility axis, endometrial cyclic changes, nutritional status, genetics and other factors, women usually have a regular menstrual cycle, is every two months, the number of days of menstruation, the amount of menstrual blood, ovarian ovulation are normal, this situation should be considered normal. If a woman’s menstrual cycle used to be once a month, and then she suddenly has her period once every two months, then she should consider that her menstrual cycle is irregular, which is an abnormal phenomenon, and may be related to endocrine disorders, polycystic ovary syndrome, and so on. Women are advised to go to the hospital for examination and let the professional doctor determine whether the menstruation is normal or not.