The common reasons for delayed menstruation without pregnancy include endocrine disorders, disease factors, dieting, medication factors and so on. 1. Endocrine disorders: endocrine disorders may cause delayed menstruation if there is too much mental stress or poor mood, environmental changes, too much anxiety and depression. 2. Disease factors: If you suffer from premature ovarian failure, polycystic ovary syndrome or pituitary tumor, hypothyroidism, endometrial adhesions and other diseases, it may also cause menstrual disorders and delayed menstruation. 3. Dieting: When dieting excessively for weight loss, the rapid weight loss, due to the central nervous system is extremely sensitive to it, may lead to hormone level disorders, menstruation delay, or even amenorrhea. 4. Drugs: If a woman takes birth control pills such as levonorgestrel tablets for a long time, it may lead to delayed menstruation. Once the symptoms of delayed menstruation appear, it is recommended to consult a doctor in a timely manner, complete the relevant examinations, identify the cause of the disease, and actively deal with it under the guidance of specialists, so as to avoid delaying the condition.