Usually, menstrual bleeding lasts about 4 to 5 days and the amount of blood lost is small (2 to 3 tablespoons). However, women who have menorrhagia usually bleed for more than 7 days and lose twice as much blood. If you have bleeding that lasts longer than 7 days per period, or is so heavy that you have to change your pad or tampon nearly every hour, you need to talk with your doctor. To find out if you have menorrhagia, your doctor will ask you about your medical history and menstrual cycles.