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  • Vitamin B12 Deficiency

    (Vitamin B12 Dependency; Macrocytic Achylic Anemia)


    Vitamin B12 deficiency can occur when the body needs more vitamin B12 than it receives from the diet. Alternatively, the condition may occur when the body is unable to use the vitamin B12 from the diet. A shortage of vitamin B12 can lead to anemia . Anemia is the insufficient delivery of oxygen by red blood cells from the lungs to the cells of the body. The sooner this anemia is treated, the more favorable the outcome. If you suspect you have this condition, contact your doctor immediately.
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    There are many causes of vitamin B12 deficiency. Some are listed below.
    • Removal of part of the small intestine or stomach
    • Advancing age
    • Long-term use of certain acid-reducing stomach medications:
      • H2 blockers
      • Proton pump inhibitors
      Atrophic gastritis (inflammation of the stomach) due to: Disorders affecting vitamin absorption: Inadequate intake of vitamin B12
      • Long-term veganism (nonconsumption of animal products) or vegetarianism
      • Breastfed infants of vegan or vegetarian mothers
      • Poor infant nutrition
      • Inadequate nutrition for a pregnant woman
      • Chronic alcohol abuse
      Stillness of the intestinal contents which can be caused by:
      • Abnormal narrowness of intestines
      • Pockets in intestines
      • Connections between loops of the intestine
      • Blind intestinal loops
      Intestinal blockage which can be caused by:
    • Inflammation of the intestine due to radiation treatment
    • Inability to use vitamin B12:
      • Lack of a needed enzyme
      • Cancer
      • Malnutrition
      • Nonfunctioning transport protein
      Increased need of vitamin B12: Over-use of nitrous oxide:
      • Frequent use
      • Extended single use of nitrous oxide (more than six hours)
      Metabolic disorders:

    Risk Factors

    A risk factor is something that increases your chance of getting a disease or condition. The following factors increase your chance of developing vitamin B12 deficiency. If you have any of these risk factors, tell your doctor:
    • Alcoholism
    • Use of certain drugs:
      • Biguanides for diabetes
      • Para-aminosalicylic acid for tuberculosis
      • Calcium-chelating drugs taken by mouth
      • Colchicine
      • Neomycin
      • Cimetidine
      • Cholestyramine
    • Age: over 50 years old
    • Strict vegan or vegetarian diet


    The symptoms of pernicious anemia can vary from person-to-person. Symptoms may change or worsen over time. If you experience any of these symptoms, do not assume it is due to this anemia. These symptoms may be caused by other health conditions. If you experience any one of them, see your physician.
    Symptoms can include:
    • Sensation of pins and needles in feet or hands
    • Alternating constipation and diarrhea
    • Stinging sensation on the tongue or smooth red tongue
    • Substantial weight loss
    • Inability to distinguish the colors yellow and blue
    • Tiredness
    • Paleness
    • Loss of hunger
    • Altered sense of taste
    • Confusion
    • Depression
    • Impaired sense of balance, especially in the dark
    • Ringing in the ears
    • Cracked lips
    • Yellow skin
    • Fever
    • Inability to sense vibrations in feet or legs
    • Dizziness when changing to standing position
    • Rapid heart rate


    Your doctor will ask about your symptoms and medical history, and perform a physical exam. Tests may include the following:
    • Complete blood count (CBC)—a count of the number of red and white blood cells in a blood sample
    • Vitamin B12 level—a test that measures the amount of vitamin B12 in the blood
    • Methylmalonic acid (MMA) level—a measurement of the amount of methylmalonic acid in the blood; this test determines whether a vitamin B12 deficiency exists.
    • Homocysteine level—a test that measures the amount of homocysteine in the blood (homocysteine is a building block of protein). The homocysteine level will be elevated if there is a shortage of vitamin B12, folate, or vitamin B-6.
    • Schilling test—a test in which a harmless amount of radiation is used to assess whether a vitamin B12 deficiency exists (rarely used)
    • Red blood cell folate level—a measurement of the amount of a B vitamin called folate
    • Gastrin level—a test that may help determine the cause of a vitamin B12 deficiency
    • Intrinsic factor assay—a measurement of the amount of a protein called intrinsic factor normally produced in the stomach; this test helps to rule out pernicious anemia as the cause of symptoms.
    • Bone marrow staining—a test that shows whether an iron deficiency exists


    Talk with your doctor about the best treatment plan for you. Treatment options include the following:

    Oral Vitamin B12 Supplement

    This treatment consists of high doses of an oral vitamin B12 supplement.

    Vitamin B12 Injections

    The doctor may advise the patient to receive injections of vitamin B12 into a muscle. Injections of vitamin B12 may be given 2-4 days per week. When blood tests show improvement, the doctor may give injections on a monthly basis.

    Treatment With Antibiotics

    This type of medication may be needed in cases where bacterial overgrowth in the intestines exists. The bacteria compete with the body to absorb the vitamin B12 in the intestines.

    Intranasal Vitamin B12

    The doctor gives the patient a supplement of vitamin B12 that is placed in the nose.

    Oral Iron Therapy

    The physician will recommend this treatment when an iron deficiency exists. In this case, the doctor will tell the patient to take iron supplements before treating with vitamin B12.


    To help reduce your chances of developing a deficiency of vitamin B12, take the following steps:
    • Avoid long-term over-consumption of alcohol.
    • As directed by your doctor, take a daily supplement containing vitamin B12.
      • As directed by your doctor, give vitamin B12 to your breastfed baby if you are a vegan or vegetarian.
    • Avoid overuse of nitrous oxide.
    • Seek diagnosis and treatment of any suspected tapeworm infestation.
    • Have your doctor check you for iron deficiency.
    • Undergo testing if your doctor suspects you are infected with the bacterium Helicobacter pylori .
    • Have your doctor monitor your health closely if you are taking the following drugs:
      • Biguanides
      • Aminosalicylic acid
      • Calcium-chelating drugs taken by mouth
      • Colchicine
      • Neomycin
      • Cimetidine
      • Cholestyramine


    American Academy of Family Physicians http://www.aafp.org/

    National Institutes of Health Office of Dietary Supplements http://ods.od.nih.gov/


    College of Family Physicians Canada http://www.cfpc.ca/

    Health Canada http://www.hc-sc.gc.ca/index%5Fe.html/


    Beers MH, Porter RS, Jones TV, eds. The Merck Manual of Diagnosis and Therapy . 18th ed. Whitehouse Station, NJ: Merck Research Laboratories; 2006.

    Beers MH, Berkow R, eds. The Merck Manual of Diagnosis and Therapy . 17th ed. Whitehouse Station, NJ: Merck Research Laboratories; 1999.

    DynaMed Editorial Team. Pernicious anemia. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php . Updated April 27, 2010. Accessed November 11, 2010.

    Kasper DL, Braunwald E, Fauci AS, eds. Harrison’s Principles of Internal Medicine . 16th ed. New York, NY: McGraw-Hill Companies, Inc; 2005.

    Morrison G, Hark L, eds. Medical Nutrition and Disease . 2nd ed. Malden, MA: Blackwell Science, Inc; 1999.

    Stipanuk MH. Biochemical and physiological aspects of human nutrition . Philadelphia, PA: WB Saunders Company; 2000.

    Whitney EN, Rolfes SR. Understanding Nutrition . 9th ed. Belmont, CA: West/Wadsworth; 2002.

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