Anemia Causes

Anemia occurs when a person has fewer RBCs than normal. This can happen for three main reasons:
Red blood cells are being lost.
The body is producing RBCs slower than it should.
RBCs are being destroyed by the body.

Causes of common types of anemia include the following:

Anemia from bleeding: Loss of blood through heavy menstrual bleeding or, wounds can cause anemia. Gastrointestinal ulcers or cancers such as cancer of the colon may slowly ooze blood and can also cause anemia.

Iron deficiency anemia: The bone marrow needs iron to make hemoglobin. Without adequate iron, your body can't produce enough hemoglobin for red blood cells. So iron plays an important role in the proper structure of the hemoglobin molecule. If iron intake is limited or inadequate due to poor dietary intake, anemia may occur as a result. This is called iron deficiency anemia.

Vitamin deficiency anemia: In addition to iron, your body needs folate and vitamin B-12 to produce sufficient numbers of healthy red blood cells. A diet lacking in these and other key nutrients can cause decreased red blood cell production. People who have an intestinal disorder that affects the absorption of nutrients are prone to this type of anemia. Some people are unable to absorb vitamin B-12 for a variety of reasons and develop vitamin B-12 deficiency anemia, which is sometimes called pernicious anemia. Vitamin deficiency anemias fall into a group of anemias called megaloblastic anemias, in which the bone marrow produces large, abnormal red blood cells.

Anemia of chronic disease: Certain chronic diseases, such as cancer, rheumatoid arthritis, Crohn's disease and other chronic inflammatory diseases can interfere with the production of red blood cells, resulting in chronic anemia. Kidney failure also can be a cause of anemia.

Anemia related to kidney disease: The kidneys release a hormone called the erythropoietin that helps the bone marrow make red blood cells. In people with chronic (long-standing) kidney disease, the production of this hormone is diminished, and this in turn diminishes the production of red blood cells, causing anemia. This is called anemia related to chronic kidney disease.

Aplastic anemia: This is a life-threatening anemia caused by a decrease in the bone marrow's ability to produce all three types of blood cells — red blood cells, white blood cells and platelets. Many times, the cause of aplastic anemia is unknown, but it's believed to often be an autoimmune disease. Some factors that can be responsible for this type of anemia include chemotherapy, radiation therapy, environmental toxins, pregnancy and lupus.

Alcoholism: Poor nutrition and deficiencies of vitamins and minerals are associated with alcoholism. Alcohol itself may also be toxic to the bone marrow and may slow down the red blood cell production. The combination of these factors may lead to anemia in alcoholics.

Bone marrow-related anemia: A variety of diseases, such as leukemia and myelodysplasia, a pre-leukemic condition, can cause anemia by affecting blood production in the bone marrow. Some blood cancers such as leukemia or lymphomas can alter the production of red blood cells and result in anemia.

Hemolytic anemia: This group of anemias develops when red blood cells are destroyed faster than bone marrow can replace them. Certain blood diseases can cause increased red blood cell destruction. Autoimmune disorders can cause your body to produce antibodies to red blood cells, destroying them prematurely. Certain medications, such as some antibiotics used to treat infections, also can break down red blood cells. Hemolytic anemias may cause yellowing of the skin and an enlarged spleen.

Sickle cell anemia: This inherited and sometimes serious anemia, which affects mainly people of African and Arabic descent, is caused by a defective form of hemoglobin that forces red blood cells to assume an abnormal crescent (sickle) shape. These irregular-shaped red blood cells die prematurely, resulting in a chronic shortage of red blood cells. Sickle-shaped red blood cells can also block blood flow through small blood vessels in the body, producing other, often painful, symptoms.

Thalassemia: this is another group of hemoglobin-related causes of anemia. There are many types of thalassemia, which vary in severity. These are also hereditary, but they cause quantitative hemoglobin abnormalities, meaning an insufficient number of hemoglobin molecules is made.

Anemia can also be caused by a combination of factors. Anemia is very common in people with cancer. In fact, about half of people with cancer develop anemia. It can have a variety of different causes, including chemotherapy or radiation therapy, which damage the bone marrow where red blood cells are produced; tumours in the bone marrow; blood loss; poor nutrition; or a combination of these reasons.