How Many Days Delay In Periods Is Normal?

I am 15 days delay in periods What is treatment for this problem

Few days delay in periods is normal. Menstrual cycle length can be of 26-32 days with an average of 28 days. A cycle of more than 35 days or less than  21 days is not normal. So, you have to wait for maximum 35 days between 2 periods. If you do not get periods even after 35 days gap then get advice from the doctor.