When a girl has her period, she is menstruating, and the menstrual period usually lasts from 2 to 8 days. Menstruation is the cyclical shedding and bleeding of the uterine lining that occurs along with the cyclical changes in the ovaries. The duration of each period is called the menstrual period, which usually lasts 2-8 days, with an average of 4-6 days. The exact period varies from person to person. Normal menstruation is cyclical and self-limiting. It usually lasts from 21 to 35 days, with an average of 28 days. The total amount of blood loss during a menstrual period is called the menstrual flow, which is normally 20~60 ml. If there is a prolongation of the menstrual period, a change in the cycle, or an increase or decrease in the amount of menstrual flow, attention should be paid to the possible presence of gynecological diseases such as uterine fibroids. If there is any discomfort, it is recommended to consult a doctor promptly for diagnosis and treatment.