The age of menarche varies from 13 to 14 years old due to genetics, nutrition, weight and mental factors, and may vary from 5 to 6 years old. If the first menstruation is early at the age of 11-12, and the latest at the age of 16, you may have abnormal ovarian function, and it is advisable to go to the hospital for examination. The first menstruation of girls is one of the signs of puberty, which means that the ovaries are able to secrete sufficient amount of estrogen. It is normal that menstruation may be irregular because the hypothalamus-pituitary-gonadal axis is less mature. It is recommended not to stay up late during the menstrual period to avoid affecting the secretion of hormones in the body, to avoid strenuous physical activity and to change sanitary napkins regularly.