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B12 Deficiency

<p>B12 Deficiency</p>
Dr. Constance Odom, MD Picture of Dr. Constance Odom, MD

Medically reviewed by

Written by our editorial team.

Last Edited 6 min read



Vitamin B12 is a nutrient that helps keep the body's nerve and blood cells healthy and helps make DNA, the genetic material in all cells. Vitamin B12 also helps prevent a type of anemia called megaloblastic anemia that makes people tired and weak.


Two steps are required for the body to absorb vitamin B12 from food. First, hydrochloric acid in the stomach separates vitamin B12 from the protein to which vitamin B12 is attached in food. After this, vitamin B12 combines with a protein made by the stomach called intrinsic factor and is absorbed by the body. Some people have pernicious anemia, a condition where they cannot make intrinsic factor. As a result, they have trouble absorbing vitamin B12 from all foods and dietary supplements.


Vitamin B12 can happen from a variety of things, such as Surgery that removes part of your stomach or intestines, pernicious anemia, which makes it hard for the body to absorb the vitamin, conditions affecting the small intestine like Crohn's Disease, heavy drinking, auto-immune disorders like lupus or grave's disease, and long-term use of acid reducing drugs, since stomach acids help break down the animal proteins that have vitamin B12. 


You can also get a deficiency in vitamin B12 if you're a vegan, someone who doesn't eat any animal products; including meat, milk, cheese, or eggs. Vegetarians who don't eat enough eggs or dairy products to meet their body's B12 needs may also suffer from this. 


Babies born to vegetarian mothers may also not get enough B12. The risk of a deficiency can also increase with age. 


A deficiency of B12 can lead to anemia, while a mild deficiency can cause no symptoms. But if it goes untreated, symptoms such as: 


Weakness, tiredness, or lightheadedness

Heart palpitations and shortness of breath

Pale skin

A smooth tongue

Constipation, diarrhea, a loss of appetite, or gas 

Nerve problems like numbness or tingling, muscle weakness, and problems walking

Vision loss

Mental problems like depression, memory loss, or behavioral changes 


If you think you are experiencing a vitamin B12 deficiency, you can ask your doctor for a blood test to see whether or not you need to supplement your diet with vitamins or enriched foods. 


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.


This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your physician about the risks and benefits of any treatment. Nu Image Medical may not offer the medications or services mentioned in this article.