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Vitamin B12 Deficiency

  • Cynthia M. Johnson, MA
Publication Type:


Vitamin B12 Deficiency

(Vitamin B12 Deficiency; Macrocytic Achylic Anemia)


Vitamin B12 deficiency is a low level of vitamin B12 in the body. This vitamin is found in foods like seafood, dairy, and eggs. The body uses it to make red blood cells, nerves, DNA, and carry out other functions.

Not getting enough of this vitamin can lead to anemia. This is a low level of red blood cells. Low B12 levels can also lead to problems with the nervous system.

Red Blood Cells.

Nucleus factsheet imagehttp://services.epnet.com/getimage.aspx?imageiid=72977297si2037.jpgsi2037.jpgNULLjpgsi2037.jpgNULL\\hgfiler01a\intellect\images\si2037.jpgNULL12NULL2008-11-072823907297_101008Copyright © Nucleus Medical Media, Inc.


Vitamin B12 deficiency can be caused by:

  • Problems that slow or stop the absorption of the vitamin from food, such as:
  • Not getting enough vitamin B12 in the diet due to:
    • Poor nutrition
    • A vegan or vegetarian diet
    • Being an infant who is breastfed by a vegan or vegetarian mother
  • Having an increased need for vitamin B12 due to:
    • Intestinal parasites
    • Other types of anemia
    • Growth in children and adolescents
    • Pregnancy
  • Problems with how the body breaks down food, such as:

Risk Factors

This problem is more common in older adults. Other things that may raise the risk are:

  • Being on a vegan or vegetarian diet
  • Having conditions or procedures that make it hard for the body to absorb vitamin B12, such as:
    • Surgery to remove part or all of the stomach
    • Surgery to the digestive system for weight loss (bariatric surgery)
    • Digestive tract disorders or infections
  • Taking medicines that reduce vitamin B12 absorption, such as metformin and proton pump inhibitors


Problems vary from person to person. They may also get worse over time. Common ones are:

  • A feeling of pins and needles in the feet or hands
  • A stinging feeling on the tongue or a smooth, red tongue
  • Weight loss
  • Tiredness, lightheadedness, or balance problems
  • Pale skin color
  • Changes in the way things taste
  • Mental and mood changes
  • Fast heartbeat


The doctor will ask about symptoms, past health, and diet. A physical exam will be done.

Blood tests will be done to check Vitamin B12 levels. This is enough to make the diagnosis.

More tests may be done to look for a cause.


Any underlying causes may be treated.

The goal of treatment is to increase vitamin B12 levels. This can be done with vitamin B12 replacement therapy. Vitamin B12 may be given by mouth, through nose spray, or by a shot.


The risk of this problem may be lowered by:

  • Eating foods that contain vitamin B12, such as seafood, dairy, and eggs
  • Taking vitamin B12—for those at risk for deficiency, such as vegetarians




  • Dietary supplement fact sheet: vitamin D. Office of Dietary Supplements website. Available at: https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional.
  • Langan RC, Goodbred AJ. Vitamin B12 deficiency: recognition and management. Am Fam Physician. 2017;96(6):384-389.
  • Vitamin B12 deficiency. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/vitamin-b12-deficiency.


  • Dianne Scheinberg Rishikof MS, RD, LDN
Last Updated:

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.