Excessive menstrual bleeding affects one in five women. This leaflet describes some of the problems women experience with heavy bleeding, and suggests ways of coping. It explains the treatments which your doctor or gynaecologist is likely to offer, and also mentions complementary therapies. The leaflet aims to help women make informed decisions about the treatment choices for heavy bleeding.The amount of blood lost in each period varies enormously from individual to individual. Some women lose a few teaspoonfuls and hardly notice their periods, while other women regularly lose large volumes of blood. Because of this wide variation it is impossible to define a 'normal' period in terms of the amount, length, and frequency of bleeding. A heavy period for one woman may be normal for another.However, for any individual woman, the amount of blood lost every month tends to remain relatively constant, apart from slight variations with age. It would be unusual for a woman to lose a few teaspoonfuls of blood one month and a pint of blood the next. Because the amount of blood loss is relatively constant, each individual woman tends to consider her own periods to be normal for her, and usually only worries about them or consults her doctor when she feels that her periods have changed.Doctors define menstrual bleeding as heavy (and call it menorrhagia) when periods last longer than seven days or more than 80ml of blood is lost during a period. It is possible to measure menstrual blood loss and doctors can have this done by their local hospital departments, especially if there is concern about a woman becoming anaemic. However, the way that a woman perceives the heaviness of her period is as important as any clinical measurements.ClotsWhen menstrual bleeding is heavy, clotting can also occur. Losing large clots can be extremely upsetting and even painful if they are large because they can cause cramping as they pass through the cervix. There is a simple explanation as to why these large clots are formed. All blood contains a clotting factor. To enable menstrual blood to flow freely from the uterus (womb) and leave your body without clotting, the uterus produces an anti-clotting agent. But if the menstrual loss is heavy, it is possible that the anti-clotting agent will be used up before a period has finished, so that the remaining blood is likely to form clots.What causes heavy bleeding?If your periods have changed, it's very important to see your doctor. There are a number of diseases which can cause heavy bleeding (see list below). The doctor will investigate possible causes and offer the appropriate treatment. But in about half the women with heavy bleeding, no cause can be found.Some causes of heavy menstrual bleeding1. Unexplained - for half of all cases no cause can be found.2. Contraceptive coil (IUD) - the coil can cause heavier, longer periods.3. Injectable contraception (Depo Provera) - can cause heavy or prolonged bleeding.4. Pelvic disorders :       ** Fibroids - these benign (not cancerous) growths in the muscular wall of the uterus are a     common cause  of   heavy bleeding.     ** Polyps - these benign growths of the lining of the uterus may cause heavy bleeding but     more commonly lead  to  spotting between or after periods.      ** Pelvic inflammatory disease - an infection in the reproductive tract which can cause infertility     and chronic  pain if untreated.   ** Endometriosis - a painful condition in which the lining of the uterus grows  outside the     uterus.  ** Endometrial hyperplasia - thickening of the lining of the uterus, leading to heavier bleeding.** Endometrial cancer - cancer of the lining of the uterus, causing heavy periods, bleeding     between periods and  blood-stained vaginal discharge. Rare, but more common in women     after the menopause.5. Blood and hormonal conditions:  ** Hormone imbalances - can stop ovulation (egg release) leading to build-up of     endometrium and heavier periods.      ** Hypothyroidism - an underactive thyroid gland can cause heavier periods. ** Blood clotting disorders.   ** Use of anticoagulant drugs.The menstrual cycle is affected by stress. If you are going through any kind of life crisis, it is possible that your periods may settle down once that crisis has been resolved. Meanwhile reassurance from your doctor that there is nothing seriously wrong may help you to accept this change as a common and usually temporary response to stress. For many women, however, there is no easy solution to the stress in their lives. If this is the case, you will need to decide whether you want treatment for your heavy bleeding.In all cases, the first step to take is to visit your GP and explain that your periods have changed. Once your doctor and/or gynaecologist have carried out the preliminary tests described in the next section, and you have been given the medical all clear, what happens next will largely depend on how you feel about your heavy bleeding.