A 13-day delay in menstruation can be caused by a variety of reasons, which may be irregular periods or pregnancy. Therefore, it is important for patients to combine other symptoms and tests to clarify the cause in time. A woman’s menstrual cycle usually lasts from 21-35 days, with an average of 28 days. It is normal to be about 7 days early or late, and the length of the cycle varies from person to person. However, if you have not had your period for more than 7 days, it may be delayed and you should go to the hospital for ovarian function, ultrasound and other related examinations to clarify the cause of the delay. Women of childbearing age with delayed periods for more than 10 days should first rule out the possibility of pregnancy and should go to the hospital for a blood HCG test to clarify whether they are pregnant. If it is diagnosed as delayed menstruation, patients can use some menstrual regulating medicine to regulate menstruation appropriately and should pay more attention to keep their mood relaxed in daily life. If it is pregnancy, women should have regular check-ups as early as possible according to the requirements of pregnancy care to prepare for childbirth.