It is not normal to have a period in 15 days. Normally a woman’s period should be about 21-35 days, less than 21 days is called a shortened menstrual period. If a patient has a period once every 15 days, once more and once less, this should be considered as possible ovulatory bleeding. The 15th day after a woman’s normal menstrual flow coincides with ovulation. Ovulation bleeding occurs in many patients due to a transient decrease in estrogen levels and fluctuations in the patient’s hormone levels, which can cause a small amount of exfoliation and bleeding of the endometrium. Ovulatory bleeding is very small and clears in 3-5 days, mostly without discomfort, and does not require special examination or treatment. If the bleeding is not ovulatory and it is not normal for the menstruation to come once in 15 days, it should be considered that there may be endocrine disorder factors or organic lesions causing it. In this case, it is necessary to do the corresponding examination according to the patient’s other clinical symptoms and signs to find out the cause and treat the symptoms.