A heavy period is medically defined as more than 80mls (about a third of a cup) of vaginal bleeding. This definition is not practically useful, however, as it is hard to accurately measure menstrual blood loss and it also does not consider the effect of the blood loss on the quality of life.
For these reasons, it is more helpful to consider a woman's periods heavy when she is having unacceptably frequent changing of pads or tampons, having leaks and accidents, waking at night to change pads/tampons, having poor quality of life due to the bleeding or suffering from medical complications of heavy bleeding including anaemia.
Causes of heavy periods
Heavy periods are more common at both ends of the reproductive spectrum due to hormonal factors as cycles become established for young women and cease in older women. The also occur due to structural problems in the womb including benign growths such as fibroids, a condition called adenomyosis, and polyps.
If you take blood thinning medication for a medical condition, this can also lead to heavy periods, even if your womb has no structural problems.
What can I do about heavy periods?
It is important to know that treatment is possible and will improve your bleeding and quality of life but that there can be some trial and error in finding the best treatment for your body and situation.
Younger women are less likely to have structural problems with the womb and more likely to be suitable for hormonal therapies which can be given in a number of ways, depending on clinical and patient factors. Many of these also provide reliable contraception.
If you are trying to conceive, there are also other options that are not contraceptive that can reduce your bleeding. An iron supplement can also help prevent developing anaemia (low blood counts).
While many women who have finished childbearing request a hysterectomy (removal of the womb) to cure their heavy periods, there are more modern less invasive options that in most cases remove the need for major surgery and have led to a great reduction in hysterectomy rates due to their success. These include endometrial ablation and Mirena IUD, the latter of which is a highly effective very safe hormonal therapy that reduces menstrual blood loss by over ninety percent in most users.
Where there are structural problems suspected in the womb, or the lining is thicker than it should be on ultrasound, or if there are risk factors for an abnormal lining, a minor procedure to sample the lining of the womb (either pipelle biopsy or hysteroscopy and biopsy) is usually performed before further treatment to ensure serious problems are not missed.