Menorrhagia is the medical term for menstrual periods with abnormally heavy or prolonged bleeding. Although heavy menstrual bleeding is a common concern among premenopausal women, most women don't experience blood loss severe enough to be defined as menorrhagia.
With menorrhagia, every period you have causes enough blood loss and cramping that you can't maintain your usual activities. If you have menstrual bleeding so heavy that you dread your period, talk with your doctor. There are many effective treatments for menorrhagia.