Normal menstruation is usually 3-7 days, if it is gone in 3 days, it is normal and does not require too much worry, unless the amount of menstruation is very small, less than 5ml is a small amount of menstruation. 5ml is not a good measure, commonly used ordinary sanitary napkins can soak through is more than 5ml. If you have a normal period and suddenly have a small period, you should pay attention to whether it is a small amount of bleeding after pregnancy, whether it is an early intrauterine pregnancy or an ectopic pregnancy or other pathological pregnancy, such as gravida, etc., there may be a small amount of vaginal bleeding, so you must go to the hospital in time for a checkup to rule out pregnancy. In addition, if you have recently undergone uterine operations, such as abortion or IUD removal, you should be alert to the possibility of uterine adhesions, which can seriously affect pregnancy and menstruation. Therefore, if you do not have menstruation for a long time after the operation or if you have very little menstruation for many times after the operation, which is significantly less than before, you should be alert and come to the hospital as soon as possible for examination, such as ultrasound, hysteroscopy, etc. In addition, menstruation is easily affected by external factors, such as emotions, fatigue, environmental changes, excessive dieting, etc. Also, oral emergency contraceptive pills and intramuscular contraceptive injections can reduce menstruation. Therefore, if the decrease in menstruation is accompanied by the above-mentioned conditions, it can be adjusted and observed. However, if the above-mentioned factors are removed and the menstrual flow is still extremely low for a long time, you should be alert and come to the hospital for examination as soon as possible.