Definition of Anemia - B12 deficiency:

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

Causes, incidence, and risk factors:

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.

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