What are the causes of heavy menstrual bleeding?

Almost all women, at some time in their reproductive life, experience heavy bleeding during a period. 

Each year, up to 2 million women consult their physicians about menorrhagia. 

It is the most common gynecologic complaint and the reason for two-thirds of all hysterectomies. 

A number of conditions can cause menorrhagia or contribute to the risk, although often the cause of heavy bleeding is unknown. 

In fact, no abnormalities to explain the bleeding are detected in about half of hysterectomies performed because of menorrhagia. 

It should be pointed out, however, that while up to 30% of premenopausal women complain of heavy bleeding, only 10% experience blood loss severe enough to be defined as menorrhagia. (On the other hand, some women might have menorrhagia but think it is normal. Such women are likely to have a family history of bleeding disorders and so believe that a heavy period is natural. ) 

With normal menstruation women lose about 2 ounces (60 ml) of blood or less. 

Factors Associated with a Higher Risk for Heavy Menstrual Bleeding

Certain characteristics are associated with a higher risk for menorrhagia: 

  • Being taller. 
  • Being older. (Women who are approaching menopause may experience occasional menorrhagia.) 
  • Having a higher number of pregnancies.


Dysfunctional uterine bleeding (DUB) is a general term for abnormal bleeding caused by hormonal abnormalities and is one of the primary causes of menorrhagia. 

In many cases, DUB occurs either when a girl just starting to menstruate or as women approach menopause, but it can occur at any time in during a woman's reproductive life. 


About 90% of DUB events occur when ovulation is not occurring (anovulatory DUB). 

In such cases, follicles do not properly develop and release a mature egg. 

When this happens, the corpus luteum, which is a mound of tissue that produces progesterone, does not form. 

As a result, estrogen is produced continuously, causing an overgrowth of the uterus lining. 

The period is delayed in such cases, and when it occurs menstruation can be very heavy and prolonged. 

Sometimes anovulatory DUB is due to a delay in the full maturation of the reproductive system in teenagers. 

Usually, however, the mechanisms are unknown. 


The other 10% of cases occur in women who are ovulating, but progesterone secretion is prolonged because estrogen levels are low. 

This causes irregular shedding of the uterine lining and break-through bleeding. 

Some evidence has associated ovulatory DUB with more fragile blood vessels in the uterus. 


Uterine Fibroids

Fibroids are the other important known causes of heavy menstrual bleeding 



Von Willebrand Disease and Other Bleeding Disorders

Bleeding disorders that impair blood clotting can cause heavy menstrual bleeding and, according to different studies, have been associated with between 10% and 17% of menorrhagia cases. 

Von Willebrand disease, a genetic condition, is the most common of these bleeding disorders and may be underdiagnosed in many women with unexplained menorrhagia.

Most studies, report this problem to be more common in African American than Caucasian women. 

Other rare disorders that impair blood platelets and clotting factors can also account for some cases of menorrhagia. 

Most bleeding disorders have a genetic basis and should be suspected in adolescent girls who experience heavy bleeding. 

Abnormal Blood Vessel Growth

Every month, blood vessels regrow in the uterus to replace the blood-rich uterine lining lost during menstruation. 

Abnormalities in this growth process (called arteriogenesis or angiogenesis) may occur in some women with menorrhagia. 

Some research indicates that imbalances in certain immune factors and growth hormones can affect angiogenesis and may be responsible for some cases of menorrhagia. 

Abnormalities in the Uterus

Structural problems or other abnormalities in the uterus may cause bleeding. 

They include the following. 

  • Miscarriage. An isolated instance of heavy bleeding usually after the period due date may be due to a miscarriage. If the bleeding occurs at the usual time of menstruation, however, miscarriage is less likely to be a cause. 
  • Uterine polyps. (These are small benign growths in the uterus.) 
  • Adenomyosis. This condition occurs when glands from the uterine lining become embedded in the uterine muscle. Its symptoms are nearly identical to fibroids (heavy bleeding and pain). Heavy bleeding occurs in between 36% and 70% of cases. It is most likely to develop in middle-aged women who have had many children. 
  • Endometriosis. (These are small implants of uterine tissue. They are more likely to cause pain than bleeding.) 
  • Uterine cancer. 
  • Infections or inflammation in the vagina, service, or pelvic area.

Other Medical Conditions or Medications That Cause Heavy Menstrual Bleeding

  • Certain medical disorders and drugs increase the risk for heavy bleeding. 
  • Medical conditions that may increase the risk for menorrhagia include thyroid problems, systemic lupus erythematosus, diabetes, and certain cancers and chemotherapies. 
  • Certain drugs, including anticoagulants and anti-inflammatory medications, can cause heavy bleeding. 
  • Some contraceptives, including certain oral contraceptives or the Copper T intrauterine device–an IUD, may also pose a risk for heavy bleeding. It should be noted, however, that some oral contraceptives and the progesterone-releasing IUD can be used to stop bleeding.