Menstruation once every 21 days may be normal as long as menstruation is regular, but if there are other discomforts, it may be due to a deficiency of qi and blood. If a woman has regular menstruation without discomfort, a menstrual cycle of 21-35 days is normal. However, if the patient has obvious discomfort, there may be a deficiency of qi and blood that leads to early menstruation. The etiology of pre-menstrual phase is mainly due to the injury of seven emotions or six external influences, or congenital deficiency of kidney qi, excessive fatigue, or overwork during sexual intercourse, which causes damage to the vital qi, malfunction of the kidney, liver, and spleen, and imbalance of qi and blood, resulting in damage to the Chong Ren and Ren meridians and causing irregular menstruation. People who have menstrual precession should go to the hospital for examination in time and regulate according to the examination results. Normally, you should pay attention to strengthening physical exercise, rationalize work and life, and avoid mental tension. During menstruation, it is necessary to prevent cold and dampness, avoid rain, wading, swimming, drinking cold drinks, etc., and pay attention to keeping warm.