What is a normal period for an adolescent girl?

Based on data in adolescent girls without a bleeding disorder, over 90% of girls have had their first period by age 14 and the average age of first period is age 12. Most of the periods in the first year are anovulatory it may take a few years before the periods become more regular and occur in 20-20 day cycles. Typically an adolescent period lasts about 4 days and only rarely last more than 7 days and one should expect no more than 3-4 pads a day