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Anemia Due to Excessive Bleeding

by Alan E. Lichtin, MD

Anemia from excessive bleeding results when loss of red blood cells through bleeding exceeds production of new red blood cells.

  • When blood loss is rapid, blood pressure falls, and people may be dizzy.

  • When blood loss occurs gradually, people may be tired, short of breath, and pale.

  • Stool, urine, and imaging tests may be needed to determine the source of bleeding.

  • The cause of bleeding is corrected, and transfusions and iron supplements are given if needed.

Excessive bleeding is the most common cause of anemia. When blood is lost, the body quickly pulls water from tissues outside the bloodstream in an attempt to keep the blood vessels filled. As a result, the blood is diluted, and the hematocrit (the percentage of red blood cells in the total blood volume) is reduced. Eventually, increased production of red blood cells by the bone marrow may correct the anemia. However, over time, bleeding reduces the amount of iron in the body, so that the bone marrow is not able to increase production of new red blood cells to replace those lost.

Rapid blood loss

The symptoms may be severe initially, especially if anemia develops rapidly from a sudden loss of blood, such as from an injury, surgery, childbirth, or a ruptured blood vessel. Losing large amounts of blood suddenly can create two problems:

  • Blood pressure falls because the amount of fluid left in the blood vessels is insufficient.

  • The body’s oxygen supply is drastically reduced because the number of oxygen-carrying red blood cells has decreased so quickly.

Either problem may lead to a heart attack, stroke, or death.

Chronic blood loss

Far more common than a sudden loss of blood is long-term (chronic) bleeding, which may occur from various parts of the body. Although large amounts of bleeding, such as that from nosebleeds and hemorrhoids are obvious, small amounts of bleeding may not be noticed. For example, a small amount of blood may not be visible in the stool. This type of blood loss is described as occult. If a small amount of bleeding continues for a long time, a significant amount of blood may be lost. Such gradual bleeding may occur with common disorders, such as ulcers in the stomach or small intestine and diverticulosis, polyps, or cancers in the large intestine. Other sources of chronic bleeding include kidney or bladder tumors, which may cause blood to be lost in the urine, and heavy menstrual bleeding.

Symptoms and Diagnosis

Symptoms are similar to those of other types of anemia and vary from mild to severe, depending on how much blood is lost and how rapidly. When the blood loss is rapid—over several hours or less—loss of just one third of the blood volume can be fatal. Dizziness upon sitting or standing after a period of lying down (orthostatic hypotension) is common when blood loss is rapid. When the blood loss is slower—over several weeks or longer—loss of up to two thirds of the blood volume may cause only fatigue and weakness or no symptoms at all, if the person drinks enough fluids.

Other symptoms may occur from the bleeding or the disorder that causes the bleeding. People may notice black, tarry stools if they have bleeding from the stomach or small intestine. Bleeding from the kidneys or bladder may cause red or brown urine. Women may notice long, heavy menstrual periods. Some disorders that cause chronic bleeding, such as stomach ulcers, produce discomfort. Other disorders, such as diverticulosis and intestinal cancers and polyps at an early stage, cause no symptoms.

Doctors do blood tests to detect anemia when people describe symptoms of anemia, have noticed bleeding, or both. Stool and urine are tested for blood in an effort to identify the source of bleeding. Imaging tests or endoscopy may be needed to identify the source of bleeding.


For large or rapid blood loss, the source of bleeding must be found and the bleeding stopped. Transfusion of red blood cells may be needed.

With slow or small blood loss, the body may produce enough red blood cells to correct the anemia without the need for blood transfusions. Because iron, which is required to produce red blood cells, is lost during bleeding, most people who have anemia from bleeding need to take iron supplements, usually tablets, for several months.