Varied Period Lengths: Understanding Normal Cycle Fluctuations

It is normal for menstrual cycles to vary in length from month to month. The average length of a menstrual cycle is 28 days, but cycles can range from 21 to 35 days. This means that it is normal for your periods to last for 4 days one month and up to 6 days the next month.

However, if your periods suddenly become much longer or shorter than they used to be, or if they become irregular, it is a good idea to see a doctor to rule out any underlying medical conditions.