Menorrhagia is the term for excessive menstrual bleeding i.e. blood loss greater than 80ml during a menstrual period. Population studies show that the typical menstrual blood loss is 30-40ml, and that 90% of women have losses of less than 80ml. Related conditions that may overlap with menorrhagia include:

• Metrorrhagia - irregular or frequent flow, noncyclic
• Menometrorrhagia - frequent, excessive, irregular flow (menorrhagia plus metrorrhagia)
• Polymenorrhea - frequent flow, cycles of 21 days or less
• Intermenstrual bleeding - bleeding between regular menses
• Dysfunctional uterine bleeding (DUB) - abnormal endometrial bleeding of hormonal cause and related to anovulation

Causes
Possible causes include those associated with hormone changes such as too much estrogen or prolactin, too little or poorly timed luteinizing hormone, and polycystic ovarian disease. Physical causes include obesity or the presence of fibroids, endometrial hyperplasia, polyps, cancer, endometriosis, ectopic pregnancy, and IUD use. Bleeding disorders such as a deficiency of vitamin K or the use of blood thinners can be contributing factors. hypothyroidism, iron deficiency, and vitamin A deficiency.

When it has been determined that the cause is not organic (a physical condition), laboratory testing (bleeding time, complete blood count, and thyroid function) should be done, and any abnormalities corrected. Heavy bleeding can be caused by too much estrogen or possibly too little progesterone. Too much estrogen causes excessive growth of the blood rich endometrial lining which will be shed each month.

Determining your blood loss
Studies that have measured blood loss have demonstrated that patients with menorrhagia have a considerable increase in menstrual blood flow during the first three days (up to 92% of their total menses being lost at this time). This suggests that the mechanisms responsible for cessation of menstruation are as effective in women who have menorrhagia as in normal women, despite the very high blood loss.

Although many women can tell if their blood loss is more or less than usual, it is difficult to accurately determine the actual blood loss using estimates based on the number of tampons or pads used. One study showed that 26% of women with normal menstrual loss considered their periods heavy, while 40% of those with heavy losses considered their periods to be moderate or light. [Acta Obstet Gynecol Scand 1966; 45: pp.320-351]