The typical menstrual cycle for adult women lasts 28 days, but it can range from 21 to 35 days, reports Womenshealth.gov. Teenage girls may have a menstrual cycle that lasts from 21 to 45 days.
Most women have their menstrual period for three to five days, although up to seven days is considered normal, notes Womenshealth.gov. This monthly cycle is a sign that a woman’s body is functioning normally. Some menstrual cycles are regular, with consistent schedules, menstrual flows and pain levels, explains Mayo Clinic, although some women experience irregular cycles. The causes of an irregular period include pregnancy, eating disorders and birth control pills.