With plentiful and prolonged menstruation (menorrhagia) too much blood is lost. Normally some women lose more blood than others, bleeding lasts about 5 days with the greatest blood loss in the first 3 days. Refer to this app if your period lasts longer, if they suddenly became abundant, if conventional sanitary napkins (or tampons) are not enough. Unusually heavy period can be caused by variety of factors, most often the cause may be a disease of the mucous membrane of the uterus and an endometrial contraceptive (spiral). But whatever the reason for the alleged plentiful menstruation - consult your doctor for treatment as plentiful regular menstrual periods may develop anemia.