There is a broad range of "normal" among menstruating women. Unpredictable or long menstrual cycles are normal for teenagers and women in their 40s. For teens, a normal cycle can be as short as 21 days or as long as 45 days. If you are a teen, you can expect cycles to even out over time. If you are nearing the age of menopause, you can expect menstrual cycles to become longer and eventually to stop. If you are not a teen or older than 40 and your cycles are shorter than 21 days or longer than 35 days, there is a chance that you have a problem that needs to be checked by your doctor.

You will need a medical check by a health professional if you have any change in your menstrual pattern or amount of bleeding that affects your daily life. This includes menstrual bleeding, for three or more menstrual cycles, that:

• Lasts longer than 7 days.
• Is a sudden or big change from your usual period.
• Is very heavy. This means that you are passing large clots or soaking through your usual pads or tampons each hour for 2 or more hours.

Other symptoms you need to have checked include:

• Bleeding between menstrual periods.
• Pelvic pain that is not linked to menstrual bleeding and lasts longer than a day.

If you are a teenage girl, see your doctor if you have not started having periods by age 15.

For more information, see the topics Abnormal Vaginal Bleeding and Dysfunctional Uterine Bleeding.