Health Encyclopedia

Anemia - B12 deficiency

Definition

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

Alternative Names

Macrocytic anemia

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 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.

Symptoms

Loss of appetite
Diarrhea
Numbness and tingling of hands and feet
Paleness
Shortness of breath
Fatigue
Weakness
Sore mouth and tongue
Confusion or change in mental status in severe or advanced cases

Signs and tests

A physical exam may show problems with reflexes or positive Babinski reflex.

The following tests will be done:

Treatment

Treatment depends on the specific cause of B12 deficiency anemia.

Pernicious anemia requires lifelong vitamin B12 injections. Those with anemia due to a lack of vitamin B12 may be told to take vitamin supplements and to follow a more balanced diet. It may be treated initially with vitamin B12 injections.

Anemia caused by malabsorption is treated with vitamin B12 injections until the condition improves.

Expectations (prognosis)

Treatment for this form of anemia is usually effective.

Complications

The signs and symptoms related to the central nervous system may be irreversible if treatment is not begun within 6 months of when these symptoms begin.
Vitamin B12 affects epithelial cells (cells that form the outer surface of the body and line inner passageways). Therefore, a lack of B12 may cause a false-positive Pap smear.

Calling your health care provider

Call your health care provider if you have any of the symptoms of anemia.

Prevention

Anemia caused by a lack of vitamin B12 can be prevented by following a well-balanced diet. B12 injections can prevent anemia after surgeries known to cause vitamin B12 deficiency. Early diagnosis and prompt treatment can limit the severity and complications of this anemia.

References

Chapman IM. Nutritional disorders in the elderly. Med Clin North Am. Sept 2006; 90(5): 887-907.

Rakel RE. Textbook of Family Practice. 6th ed. Philadelphia, Pa: WB Saunders; 2005:1232.

Review Date:2/14/2007
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.

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