Anemia - B12 deficiency

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Megaloblastic anemia - view of red blood cells

B12 deficiency anemia is a drop in the number of red blood cells due to a lack of vitamin B12.

Macrocytic anemia

Vitamin B12 is essential for normal nervous system function and blood cell production. The main sources of vitamin B12 include meat, eggs, and dairy products. For vitamin B12 to be absorbed by the body, it must bind to intrinsic factor, a protein secreted by cells in the stomach.

Causes of vitamin B12 deficiency include:

• A diet low in vitamin B12 (for example, a strict vegetarian diet that excludes all meat, fish, dairy products, and eggs)
• Chronic alcoholism
• Abdominal or intestinal surgery that affects intrinsic factor production or absorption
• Crohn's disease
• Intestinal malabsorption disorders
• Fish tape worm
• Pernicious anemia , which is caused by a lack of intrinsic factor

The risk factors are related to the causes.

Review Date: 01/26/2005
Reviewed By: William Matsui, MD, Assistant Professor of Oncology, Division of Hematologic Malignancies, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD. Review provided by VeriMed Healthcare Network.