Definition of Anemia - B12 deficiency:

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

Causes, incidence, and risk factors:

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 sufficiently absorbed by the body, it must bind to intrinsic factor, a protein released by cells in the stomach. The combination of vitamin B12 bound to intrinsic factor is absorbed in the final part of the small intestine.

Causes of vitamin B12 deficiency include:

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

The risk factors are related to the causes.