Carl R. Darnall Army Medical Center - Health Library

Vitamin B12 Deficiency

(Vitamin B12 Deficiency; Macrocytic Achylic Anemia)

Pronounced: Vite-ah-min bee-twelv di-fish-ens-ee

Definition

Vitamin B12 has many important roles in the body. It helps to make red blood cells, build DNA, and maintains a protective coating around the nerves.

Vitamin B12 deficiency is a shortage of available B12 in the body. It can occur when:

  • The body needs more vitamin B12 than it gets from the diet
  • The body is unable to absorb enough vitamin B12 from the diet

A deficiency in vitamin B12 can lead to:

  • Anemia—low levels of red blood cells. Red blood cells carry oxygen throughout the body. Anemia can make you feel tired and weak.
  • Problems with the nervous system—as nerves lose their protective coating.

Red Blood Cells
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Causes ^

There are many causes of vitamin B12 deficiency, such as:

  • Conditions that slow or stop the absorption of the vitamin from food:
  • Not eating enough foods vitamin B12
    • Long-term veganism or vegetarianism
    • Breastfed infants of vegan or vegetarian mothers
    • Poor nutrition
    • Inadequate nutrition for a pregnant woman
  • Greater need for vitamin B12:
    • Intestinal parasites
    • Other types of anemia
    • Growth in children and adolescents
    • Pregnancy
  • Metabolic disorders—problem with how the body breaks down food:

Risk Factors ^

The following factors increase your chance of developing vitamin B12 deficiency:

  • Alcoholism
  • Use of certain drugs:
    • Biguanides for diabetes
    • Acid-reducing medications
  • Strict vegan or vegetarian diet

Symptoms ^

The symptoms can vary from person-to-person and may change or worsen over time. Symptoms can include:

  • Sensation of pins and needles in feet or hands
  • Stinging sensation on the tongue or smooth red tongue
  • Substantial weight loss
  • Tiredness
  • Paleness
  • Altered sense of taste
  • Confusion
  • Depression
  • Impaired sense of balance, especially in the dark
  • Inability to sense vibrations in feet or legs
  • Lightheadedness when changing to standing position
  • Rapid heart rate

Diagnosis ^

You will be asked about your symptoms and medical history. A physical exam will be done. Tests may include the following:

  • Complete blood count (CBC)—a count of the number of specific 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
  • Homocysteine level
  • Folate level—a measurement of the amount of a B vitamin called folic acid
  • Intrinsic factor antibodies—this test helps to determine anemia as the cause of symptoms

Treatment ^

Treatment options include the following:

Oral Vitamin B12 Supplement

Daily high doses of an oral vitamin B12 supplement may help improve levels in the body. These dosages should only be given under a doctor's care.

Vitamin B12 Injections

The doctor may advise injections of vitamin B12 into a muscle. Injections of vitamin B12 may be given frequently at first. When blood tests show improvement, the injections may be given on a monthly basis.

Intranasal Vitamin B12

This form of vitamin B12 supplement is as a spray through the nose.

Treatment with Antibiotics

A bacterial overgrowth in the intestines can slow or stop the absorption of B12. Antibiotics may help to control the bacteria and improve vitamin levels in the body.

Prevention ^

To help reduce your chances of developing a deficiency of vitamin B12, take the following steps:

  • Include foods that are a source of vitamin B12, such as:
    • Eggs, milk, cheese, and milk products
    • Meat, fish, shellfish, and poultry
    • Soy-based meat substitutes
    • Some soy and rice beverages
  • 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.
  • Have your doctor monitor your health closely if you are taking certain medications:
    • Biguanides
    • Acid-reducing medications
RESOURCES:

Family Doctor—American Academy of Family Physicians
http://familydoctor.org

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

CANADIAN RESOURCES:

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

Health Canada
https://www.canada.ca

REFERENCES:

Food sources of vitamin B12. Dietitians of Canada website. Available at: https://www.dietitians.ca/Your-Health/Nutrition-A-Z/Vitamins/Food-Sources-of-Vitamin-B12.aspx. Accessed November 7, 2017.

Pernicious anemia. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T116294/Pernicious-anemia. Updated May 17, 2017. Accessed November 7, 2017.

Vitamin B12. American Association of Clinical Chemistry—Lab Tests Online website. Available at: http://www.labtestsonline.org/understanding/analytes/vitamin_b12/glance.html. Updated April 24, 2015. Accessed November 7, 2017.

Vitamin B12. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T233168/Vitamin-B12. Updated November 6, 2017. Accessed November 7, 2017.

Vitamin B12 deficiency. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T116899. Updated December 4, 2015. Accessed November 7, 2017.

Last reviewed January 2018 by EBSCO Medical Review BoardDianne Scheinberg Rishikof MS, RD, LDN  Last Updated: 2/6/2018