A 15-day delay in menstruation is more abnormal. The normal menstrual cycle for women is 21-35 days. It is normal if the period is occasionally 7 days early or 7 days late, but it is abnormal if it is delayed for 15 days. In the case of adolescent and menopausal women who may have irregular menstruation and have a 15-day delay in menstruation, they can continue to observe and do not need to be treated. However, if a woman of childbearing age who usually has regular periods experiences a delay of 15 days in her periods and also has a recent history of sexual intercourse, she should be tested with an early pregnancy test or have her blood hCG checked to determine if she is pregnant. If there is no pregnancy, it is most likely due to diseases such as dysfunctional uterine bleeding, amenorrhea, polycystic ovary syndrome, hyperprolactinemia, etc. Relevant tests should be performed to further confirm the diagnosis. If there is only one case of delayed menstruation for 15 days, there is no need to worry too much and you can observe it first. However, if you have irregular menstruation for a long time, you need to visit a gynecologist in time to clarify the cause and treat the problem.