Staying up late may cause delayed menstruation. The menstrual cycle is usually 28-30 days, with an average of 28 days. 7 days early or late is the normal range. However, a period is delayed if it does not occur beyond 7 days. In case of delayed menstruation, if a woman has recently had sex, pregnancy can be ruled out first by early pregnancy test or blood HCG test. Menstruation can be affected by many factors, such as emotions, locality, season, weather, staying up late, etc., which may delay menstruation. Staying up late occasionally usually does not affect menstrual changes, but staying up late for a long time will disturb the balance of the body’s internal environment and affect the brain’s secretion of hormones, thus causing endocrine disorders and affecting ovarian function, resulting in delayed menstruation, which may seriously lead to menopause. A comprehensive examination should be performed to find the cause of delayed menstruation. If there is no organic lesion and there is no problem with the whole endocrine axis, it may be a problem of living habits, such as staying up late for a long time, or large mood swings. Therefore, women should try to maintain good living habits and a happy mood, avoid staying up late, have a balanced diet and exercise in moderation on a daily basis.