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Anemia - B12 deficiency

  • Alternative Names

    Macrocytic anemia


    Treatment depends on the cause of B12 deficiency anemia.

    • Pernicious anemia requires lifelong vitamin B12 replacement, most often using injections. Some patients can get enough supplementation with high-dose tablets of oral vitamin B12.
    • People with anemia due to a lack of dietary vitamin B12 may be told to take vitamin supplements and follow a more balanced diet. Treatment may start with vitamin B12 injections.
    • Anemia caused by poor digestion and absorption is treated with vitamin B12 injections until the condition improves. These shots are given every day and then every week at first, and then every month.

    Many people may need these shots once a month for the rest of their life. The shots may no longer be needed after Crohn's disease, celiac disease, or alcoholism is properly treated.

    Support Groups

    Expectations (prognosis)

    Treatment for this form of anemia is usually effective.

    Any damage to nerves may be permanent, especially if treatment is not started within 6 months of when the symptoms begin.


    Vitamin B12 affects cells that form the outer surface of the body and line inner passageways (epithelial cells). Therefore, a lack of B12 may cause a falsely abnormal Pap smear.

    Calling your health care provider

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