Heavy Periods (Bleeding) – Meaning, Causes and Dangers

It is a common menstrual problem that many women experience occasionally and for some women it is a monthly experience. Apart from theĀ  heavy flow the duration of the bleed may also be prolonged. This is known as menorrhagia and may occur for many different reasons. While this can occur with the use of certain medication and gynecological conditions like uterine fibroids, sometimes menorrhagia may be a sign of serious and even life-threatening conditions like uterine cancer.

Read more on menorrhagia.

How Do Periods Become Heavy?

In order to understand why periods may be heavy and prolonged, it is important to first understand how menstrual bleeding occurs. The menstrual cycle is controlled by different hormones and specifically four hormones. Two of these hormones – follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are secreted by the pituitary gland located at the base of the brain. The other two hormones – estrogen and progresterone – are primarily secreted by the ovaries in the pelvis.

FSH and LH stimulate the ovaries to secrete estrogen and progesterone. Estrogen causes the inner lining of the uterus (endometrium) to thicken. Progrestrone causes the endometrium to mature. If an ovum (egg cell) is not fertilized then the estrogen and progresterone decreases. The drop in hormone levels then causes the endometrium sloughs off and is passed out with blood through the vagina. This is known as menstruation and the bleeding can last for 2 to 7 days.

What do heavy periods mean?

There are several reasons why bleeding may be heavier or even longer than normal. Firstly bleeding may not be stopped as would be normally expected. This is seen with clotting disorders where the body’s ability to form clots and halt bleeding is impaired.

Secondly a disturbance in the hormone levels can also lead to heavy menstrual bleeding. For example, if there is no ovulation then there may be no progesterone secretion which allows estrogen to act to a greater extent than normal. This may lead to excessive endometrial thickening and ultimately heavier bleeding.

Are heavy periods normal?

Along with painful periods, heavy menstrual bleeding is sometimes believed to be normal for some young girls and women. It is also incorrectly thought that the pain and heaviness of the bleed will resolve after the first pregnancy. Therefore medical treatment is not sought immediately. These are misconceptions and medical treatment should be sought as soon as possible.

Causes of Heavy Period Bleeding

Most of the causes of heavy bleeding during periods are discussed below. It is important to differentiate vaginal bleeding from bleeding arising from the urinary tract or even the rectum. Vaginal bleeding can occur during pregnancy and this may be a sign of a threatened miscarriage or an ectopic pregnancy. Sometimes a single heavy period can be a sign of a miscarriage.

Read more on abnormal vaginal bleeding.


Infections of the reproductive organs (pelvic inflammatory disease) or urinary tract (UTI) can be one cause of heavy or prolonged periods. Some of these infections may be sexually transmitted. The bleeding may not always be heavy but some women will report it as being a period that is different from their regular periods. In women who are not menstruating, such as in postmenopausal women, bleeding from the urethra and rectum must be considered.

Bleeding Disorders

Heavy periods can be related to bleeding disorders without any abnormality of the menstrual cycle or female reproductive organs. Usually athere is a family history of bleeding disorders and heavy periods since the first period (menarche). In most cases a menstruating girl or woman would know about their bleeding disorder which may include von Willebrand disease, hemophilia, prothrombin deficiency and other clotting problems.

Hormone Imbalance

Various endocrine disorders may contribute to heavy periods. This is a problem with the glands and/or the levels of the hormones that it secretes. Menorrhagia may occur with both hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid). High insulin levels (hyperinsulinemia) may also cause heavy periods.

Problems with the pituitary gland may affect gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), luteinizing hormone (LH) and prolactin, all of which can lead to heavy bleeding. Elevated androgen (male hormone) levels which may occur with polycystic ovarian syndrome (PCOS) can also lead to heavy bleeding.

Abnormal Growths

Uterine fibroids and uterine polyps are two types of growths that can lead to heavy periods. These growths are usually benign (non-cancerous). Fibroids are growths within the muscular layer of the uterus wall while polyps are protruding growths from the inner uterine layer.

Adenomyosis is where glands of the endomentrium abnormally grow into the inner muscle layer of the uterus and causes heavy bleeding along with severe period pain. Cancer is another type abnormal growth. Cervical, uterine and ovarian cancer may also lead to heavy periods but this is rare.


Various medication can lead to heavy periods. Blood thinners are the most obvious as it impairs blood clotting. Steroid drugs and cancer-treating drugs (chemotherapy) can also contribute to heavy periods. An intra-uterine device (IUD) may also cause heavy periods in some women although it should reduce menstrual bleeding and even stop periods altogether.

Organ Failure

Heavy periods may occur with both liver and kidney failure even when there is no abnormality of the female reproductive organs. In liver failure the production of clotting factors is affected which can then lead to bleeding disorders. With kidney failure there is often a complete cessation of periods (amenorrhea) but some women experience heavy periods instead.

Dangers of Heavy Periods

Most of the time heavy periods do not cause serious complications. Iron-deficiency anemia is the most common complication of heavy periods. In fact most cases of anemia in girls and women of reproductive age is due to heavy periods. However, when the bleeding is severe and persistent then it can lead to more serious complications such as palpitations and shortness of breath. This requires immediate medical attention as it can complicate underlying conditions and pre-existing diseases which could even prove to be life-threatening in rare cases.

Read more on how heavy periods are treated.


  1. www.mayoclinic.org/diseases-conditions/menorrhagia/basics/definition/con-20021959
  2. emedicine.medscape.com/article/255540-overview

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