Cause: Many possible causes, including low Iron levels.

Useful Supplements: Iron, Vitamin A, Vitamin C, Vitamin E.

Useful Herbs: Cinnamon, False Unicorn, Vitex.

Further information: Menorrhagia, or excessive menstrual bleeding, should always be checked by a health care professional. While its cause may be as innocuous as stress, it can also be caused by such disorders as infection, miscarriage, hormonal imbalance, thyroid disease, or cervical cancers.
In most cases, no treatment is needed, other than caution and watching for loss of large blood clots. If cramping accompanies menorrhagia, aspirin should NOT be taken, as it thins the blood and may cause further bleeding.

The following supplements and herbs may be effective in treating menorrhagia:

Iron deficiency is often found in women with menorrhagia. The cause-effect relation is uncertain, however – it may be that low iron levels cause increased bleeding, or that the increased bleeding causes a decrease of iron. In either case, iron supplementation (up to 200 mg daily) often will help slow menstrual flow.¹

Vitamin A deficiency also is quite common in women with menorrhagia. 25,000 IU taken twice daily for two weeks has been shown to cause improvement, sometimes even complete return to a normal menstrual blood flow.²

Vitamin C protects small blood vessels from damage. This may help to prevent excessive menstrual blood loss as well, as shown in one study.³

Vitamin E may also be effective in relieving menorrhagia. However, it has only been studied as a treatment for menorrhagia caused by IUD birth control devices.⁴

Cinnamon has long been used for the treatment of menstrual disorders.⁵ False Unicorn has also been used for these conditions.⁶

Vitex is probably the most effective herb in the treatment of menorrhagia. However, it needs to be used for several months before its effects are noticed. 40 drops of Vitex extract taken daily can be used for up to eighteen months continuously, unless pregnancy occurs (at which point Vitex use should be discontinued).

References:

¹Taymor ML, Sturgis SH, Yahia C. The etiological role of chronic iron deficiency in production of menorrhagia. JAMA 1964;187:323–7.
²Lithgow DM, Politzer WM. Vitamin A in the treatment of menorrhagia. S Afr Med J 1977;51:191–3.
³Cohen JD, Rubin HW. Functional menorrhagia: treatment with bioflavonoids and vitamin C. Curr Ther Res 1960;2:539.
⁴Dasgupta PR, Dutta S, Banerjee P, Majumdar S. Vitamin E (alpha tocopherol) in the management of menorrhagia associated with the use of intrauterine contraceptive devices (ICUD). Internat J Fertil 1983;28(1):55–6.
⁵Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Foods,Drugs, and Cosmetics, 2d ed. New York: John Wiley & Sons, 1996, 168–70.
⁶Mills SY. Out of the Earth: The Essential Book of Herbal Medicine. Middlesex, UK: Viking Arkana, 1991, 520–22.