Anemia - B12 deficiency

Anemia of B12 deficiency is a decrease in the number of red cells in the blood caused by a deficiency of Vitamin B12 (cyanocobalamin).

Alternative Names

Macrocytic anemia

Causes, incidence, and risk factors

Vitamin B12 is essential for normal nervous system function and normal red cell, white cell and platelet production. All sources of Vitamin B12 come from the diet in animal products, including dairy and eggs. For Vitamin B12 to be absorbed by the body, it must become bound to an intrinsic factor , a protein secreted by cells in the stomach. Causes of Vitamin B12 deficiency include dietary (a strict vegetarian diet excluding all meat, fish, dairy products, and eggs); chronic alcoholism ; abdominal or intestinal surgery that eliminates the site of intrinsic factor production or absorption; Crohn's disease ; intestinal malabsorption disorders; fish tape worm; and pernicious anemia , which is caused by a deficiency in the production of intrinsic factor. Risk factors are related to the causes. The incidence is 2 out of 1000 people.

Signs and tests

Physical evaluation of the neurological signs may show depressed deep tendon reflexes, decreased position sense, decreased vibration sense, or positive Babinski reflex.

  • CBC
  • results show low
  • hematocrit with an elevated MCV
  • bone marrow examination
  • an elevated
  • LDH
  • below normal
  • Vitamin B12 level
  • Schilling test
  • (to determine where the deficiency in B12 absorption lies).
  • Treatment

    Treatment depends on the cause of the anemia . Pernicious anemia requires life long therapy with Vitamin B12 injections. Anemia caused by dietary insufficiency of Vitamin B12 can be corrected by oral (by mouth) vitamin replacement in combination with a more balanced diet . Initially it may be treated with Vitamin B12 injections. Anemia caused by malabsorption (inadequate absorption of nutrients from the intestinal tract) is treated with Vitamin B12 injections until the condition improves.

    Expectations (prognosis)

    The anemia generally is corrected by therapy.


    Central nervous system signs and symptoms may be irreversible if treatment is not initiated within 6 months of the onset of these symptoms. Vitamin B12 affects the maturation of all epithelial cells (cells that form the outer surface of the body and line inner passageways) and a deficiency may cause a false positive pap smear .

    Calling your health care provider

    Call your health care provider if symptoms indicate anemia of Vitamin B12 deficiency.


    Anemia of B12 deficiency that is caused by a poor diet can be prevented through a well-balanced diet . Prophylactic (preventative) use of Vitamin B12 injections can prevent deficiency after surgeries known to result in Vitamin B12 deficiency. Early diagnosis and prompt treatment can limit the severity of the anemia as well as the neurologic complications.

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