It is normal for most girls to not have their periods at age 13. Many girls get their periods by the age of 11-13, and a few may get their periods around the age of 14 or 15. The timing of menstruation is related to the girl’s nutritional status, physical condition, and hormone levels. Over the years, with the improvement of living standards, the age of menstruation for girls has also advanced, and a small number of girls may have their periods around 10 years old, which is fine as long as the height and growth of women are not affected. If you are over 14 or 15 years old and have not had your period, you should go to the hospital for a checkup to see how your uterus and fallopian tubes are developing. Also, hormone levels should be checked.