Hi, thanks for using healthcare magic There are different causes for delayed periods. If you are sexually active, it would be important to rule out pregnancy first. The other causes are: (a) PCOS- this stands for polycystic ovarian syndrome. This condition is diagnosed if a women has at least 2 of the following criteria, (1) irregular or delayed periods (2) cysts on the ovaries identified on ultrasound (3) signs or symptoms of increased levels of male hormones (b) extreme physical activity (c) emotional stress (d)physical stress or illness (e)abnormal level of prolactin hormone (f)abnormal levels of thyroid hormone If your pregnancy test is negative , then you should consider visiting your doctor for an evaluation which would include physical examination and investigations for the above hormone levels. I hope this helps