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Vitamin B12 Deficiency

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Are you getting enough vitamin B12? Many people don’t, and that deficiency can cause problems.

Vitamin B12 does a lot of things for your body. It helps make your DNA and your red blood cells, for examples.

You can get vitamin B12 from your diet, or from supplements. Exactly how much you need depends on your age.

assorted vitamins

Causes of Vitamin B12 Deficiency

Vitamin B12 deficiency can happen if you have certain conditions, such as:

  • Atrophic gastritis, in which your stomach lining has thinned 
  • Pernicious anemia, which makes it hard for your body to absorb vitamin B12
  • Surgery that removed part of your stomach or small intestine, including weight loss surgery
  • Conditions affecting the small intestine, such as Crohn's disease, celiac disease, bacterial growth, or a parasite
  • Heavy drinking
  • Immune system disorders, such as Graves' disease or lupus
  • Long-term use of acid-reducing drugs

You can also get vitamin B12 deficiency if you're a vegan (meaning you don't eat any animal products, including meat, milk, cheese, and eggs) or a vegetarian who doesn't eat enough eggs or dairy products to meet your vitamin B12 needs.

Babies born to mothers who are vegetarians may also not get enough vitamin B12.

Symptoms of Vitamin B12 Deficiency

A deficiency of vitamin B12 can lead to vitamin B12 deficiency anemia. A mild deficiency may cause only mild, if any, symptoms. But if untreated, it may cause symptoms such as:

  • Weakness, tiredness, or light-headedness  
  • Rapid heartbeat and breathing
  • Pale skin
  • Sore tongue
  • Easy bruising or bleeding, including bleeding gums
  • Stomach upset and weight loss
  • Diarrhea or constipation

If you think you have symptoms of vitamin B12 deficiency, you can ask your doctor for a blood test to check on that.

Treatment for Vitamin B12 Deficiency

Vitamin B12 deficiency treatment depends on the cause. 

If pernicious anemia or a problem with absorption is the cause, you'll need to replace vitamin B12, usually by injection, or by prescription.

If the issue is that you don't eat animal products, you can change your diet or take supplements.

For most people, treatment resolves the problem. But any nerve damage that happened due to the deficiency could be permanent.

Preventing Deficiency Problems

Most people can prevent vitamin B12 deficiency by eating enough meat, poultry, seafood, dairy products, and eggs. 

If you don't eat animal products, or you have a medical condition that limits how well your body absorbs nutrients, experts recommend taking a B12-containing multivitamin and eating breakfast cereal fortified with vitamin B12.

If you're using vitamin B12 supplements, let your doctor know, so he or she can make sure they won't affect any medicines you're taking.

WebMD Medical Reference

Reviewed by Melinda Ratini, DO, MS on April 02, 2014
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