Delayed menstruation for 11 days is commonly caused by the following clinical reasons: the first one is that if you have normal sexual life, it is likely to be caused by pregnancy. The second is caused by endocrine disorders, such as recent stress in daily life, anxiety, insomnia, or changes in the environment, which may lead to endocrine disorders and delay menstruation. The third one is polycystic ovary syndrome which can lead to delayed menstruation. The fourth is due to ovarian failure, which can also delay menstruation. The fifth is delayed menstruation due to hyperprolactinemia. The sixth is due to hyperandrogenemia, which can also lead to delayed menstruation. Therefore, once menstrual delay occurs, it is necessary to combine the clinical history, give a comprehensive analysis, and do the relevant laboratory tests to make a preliminary diagnosis.