Many women feel that their periods are heavy. Doctors consider a woman's menstrual periods to be genuinely "heavy" when they meet any one of three criteria:
periods last eight days or longer
the blood flow causes you to change your sanitary napkin or tampon more than once an hour for six hours in a row or longer
there is a significant increase in the amount or number of days of your usual flow, compared with your own usual periods.
It's normal for menstrual flow and duration to vary somewhat from period to period. If you have a repeated, long-lasting increase in monthly flow then you should be evaluated by a doctor. About ten percent of women have heavy periods, also called "menorrhagia." Some of the more common causes include hormone changes, thyroid problems, growths or other changes in the uterus, problems with your blood's ability to clot, or a pelvic infection.
Heavy periods usually keep to the monthly cycle pattern. Sometimes bleeding can last or recur throughout the month and it may be hard to know when one period ends and another begins, a problem known as "menometrorrhagia." If your bleeding is not occurring in a clear monthly cycle, please visit our health guide on Bleeding Between Menstrual Periods.
The Heavy Menstrual Periods Decision Guide is designed to give you some information about what may cause monthly periods to be heavy and what steps you can take to get help. This guide is not meant to substitute for a doctor's evaluation.