Vitamin B12 Deficiency

(Vitamin B12 Deficiency; Macrocytic Achylic Anemia)

How to Say It: Vite-ah-min bee-twelv di-fish-ens-ee


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. It can also lead to problems with the nervous system.

Red Blood Cells

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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
    • Bariatric surgery
    • Digestive tract disorders or infections
  • Taking medicine that makes it hard for the body to absorb vitamin B12, 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
  • Pale skin color
  • Changes in the way things taste
  • Confusion
  • Mood changes
  • Balance problems, especially when in the dark
  • Lightheadedness when changing to standing position
  • Rapid heartbeat


The doctor will ask about your symptoms and health history. A physical exam will be done. You may also be asked about your diet.

Your level of vitamin B12 will be tested. This can be done with blood tests.

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.


The risk of this problem may be lowered by eating foods that contain vitamin B12, such as seafood, dairy, and eggs. Supplements may need to be taken by people who are at risk for deficiency, such as vegetarians.


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


College of Family Physicians of Canada


Dietary supplement fact sheet: vitamin D. Office of Dietary Supplements website. Available at: Accessed February 5, 2021.
Vitamin B12 deficiency. EBSCO DynaMed website. Available at: Accessed February 5, 2021.
Last reviewed December 2020 by EBSCO Medical Review Board Dianne Scheinberg Rishikof MS, RD, LDN
Last Updated: 2/4/2021

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