A delay in menstruation for more than 10 days is most often caused by: 1) pregnancy; 2) menstrual disorders. If your period is delayed for more than 10 days, you can take a blood HCG test to determine if the delayed period is caused by pregnancy. If the blood HCG value suggests no pregnancy, consider mood swings, mental tension, stressful work, life, study, and changes in the environment causing menstrual disorders. In this case, a gynecological ultrasound is needed to find out the endometrial condition. If the endometrium is greater than 5mm, you can consider giving Didrogestrel 10mg orally twice a day for 10 days and stopping the medication to wait for menstruation.