A woman usually has her period once a month or so, with a cycle of 28 days. A week early or a week late is considered normal, which means a period of 21-35 days is considered normal. If it comes less than once every 21 days, it is called frequent menstruation. If it comes more than once every 35 days, it is called scanty menstruation. Both of these are not normal. Normal should be between 21-35 days, and most people may be around 28-30 days, with fluctuations of a few days before and after being considered normal. However, if some people do not come for several months or come frequently, both require medical intervention, depending on what medication is needed, how long it will take, and how it is administered. Therefore, if your period is not in the 21-35 day range, you need to go to the hospital for a checkup.