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by Kahn M

Vitamin B12 Deficiency

(Vitamin B12 Deficiency; Macrocytic Achylic Anemia)


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
Nucleus factsheet image
Copyright © Nucleus Medical Media, Inc.


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


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


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 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.


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


Family Doctor—American Academy of Family Physicians
National Institutes of Health Office of Dietary Supplements


College of Family Physicians of Canada
Health Canada


Food sources of vitamin B12. Dietitians of Canada website. Available at: Accessed November 7, 2017.
Pernicious anemia. EBSCO DynaMed Plus website. Available at: . Updated May 17, 2017. Accessed November 7, 2017.
Vitamin B12. American Association of Clinical Chemistry—Lab Tests Online website. Available at: Updated April 24, 2015. Accessed November 7, 2017.
Vitamin B12. EBSCO DynaMed Plus website. Available at: . Updated November 6, 2017. Accessed November 7, 2017.
Vitamin B12 deficiency. EBSCO DynaMed Plus website. Available at: . Updated December 4, 2015. Accessed November 7, 2017.

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