If there is a sudden increase in the amount of menstruation on the fourth day of menstruation, the following causes are common in clinical practice: first, diet, such as drinking a lot of alcohol or taking blood-boosting medications, may cause a sudden increase in menstrual flow, and it is recommended to review the diet or medications used in daily life. Secondly, it is possible that this is not a menstrual period, but an abnormal vaginal bleeding, which is clinically caused by pregnancy, we suggest to take blood test for HCG to identify. Thirdly, endocrine disorders may cause a sudden increase in menstrual flow, but after examination there may be no organic lesions, it is recommended to give symptomatic treatment in a timely manner.