The most common cause is the decrease of estradiol, which leads to unclean menstruation and no repair of the endometrium, and the decrease of estradiol causes the endometrium to become thinner, which reduces the menstrual flow. It is recommended to have a blood test for sex hormone 6, usually on the 2nd-3rd day of menstruation, with the results referring to the follicular phase. In case of low estradiol, it can be supplemented clinically with medication, and eating more foods containing estrogen in daily life, such as onions, black beans and peanut butter, can supplement exogenous estrogen, which will also improve the corresponding symptoms clinically. In case of occasional menstrual irregularities and low volume, just for this month, the possibility of pregnancy should be ruled out and treatment should be given according to the results.