The number of days in the menstrual cycle is the number of days between the first day of the last menstrual period and the first day of the current period. 22-45 days apart is normal. The length of the menstrual cycle is strongly related to the time it takes for the follicles to develop and mature. Women who have a short time for follicles to mature will also have a short menstrual cycle. The length of the menstrual cycle is also controlled by the level of hormones in the body. Patients with luteal insufficiency shed early because their corpus luteum does not produce enough hormones to support the growth of the endometrium. If the menstrual cycle is less than 20 days or more than 45 days, you need to go to the gynecology department of the hospital for a clear diagnosis and then treat the symptoms. Pay attention to keep your mood relaxed, eat more vegetables and fruits, do not stay up late, and exercise properly to strengthen your body resistance.