It is not normal for a 15-year-old girl to have her period twice a month. Because the pituitary-ovarian axis is not very mature in 15-year-old girls, endocrine disorders can easily lead to twice a month menstruation. If the amount of menstruation is high, it is easy to cause anemia, so timely treatment is needed. In general, the girl should be taken to the hospital for an ultrasound examination to rule out abnormalities of the uterus, adnexa and endometrium. If there are no developmental abnormalities, a hormone level test should be performed to find out if there is polycystic ovary syndrome or other endocrine disorders. According to the test results, menstrual cycle adjustment treatment can be given by taking one tablet of Tegretol 1mg for 21 days. Progesterone 100mg twice a day for 10 days on the 11th day. Usually, menstruation will occur 3-7 days after stopping the medication, and normal menstruation may be restored after 3 consecutive cycles.