Anemia - B12 deficiency

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Megaloblastic anemia - view of red blood cells

Anemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues.

Vitamin B12 deficiency anemia is a low red blood cell count due to a lack of vitamin B12.

See also:

• Megaloblastic anemia
• Pernicious anemia

Macrocytic anemia

Your body needs vitamin B12 to make red blood cells. In order to provide vitamin B12 to your cells:

• You must eat enough foods that contain vitamin B12, such as meat, poultry, shellfish, eggs, and dairy products.
• Your body must absorb enough vitamin B12. Your body uses a special protein, called intrinsic factor, released by cells in the stomach. The combination of vitamin B12 attached to intrinsic factor is absorbed in the last part of the small intestine.

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A lack of vitamin B12 in the diet may be due to:

• Eating a vegetarian diet
• Poor diet in infancy
• Poor nutrition during pregnancy

A number of problems can make it difficult for your body to absorb enough vitamin B12:

• Chronic alcoholism
• Crohn's disease, celiac disease, infection with the fish tapeworm, or other problems that make it difficult for your body to digest foods
• Pernicious anemia, which occurs when your body destroys cells that make intrinsic factor. Intrinsic factor is needed to absorb vitamin B12.
• Surgeries that remove certain parts of your stomach or small intestine, such as some weight-loss surgeries
• Taking antacids and other heartburn medicines for a long period of time

Review Date: 01/31/2010
Reviewed By: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).