Reviewed by Brunilda Nazario, MD on July 23, 2015
Are you getting enough vitamin B12? Many people don’t, and that deficiency can cause some serious problems.
Vitamin B12 does a lot of things for your body. It helps make your DNA and your red blood cells, for examples.
Since your body doesn’t make vitamin B12, you’ll need to get it from animal-based foods or from supplements, and it needs to be consumed on a regular basis. Exactly how much you need and where you should get it from depends on things like your age, the diet you follow, your medical conditions, and in some cases what medications you take.
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. Stomach acids help break down animal proteins that have vitamin B12.
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. Vegans can take supplements containing vitamin B12 or by eating vitamin B12-fortified grains.
The risk of B12 deficiency also increases with age.
Symptoms of Vitamin B12 Deficiency
A deficiency of vitamin B12 can lead to anemia. A mild deficiency may cause no symptoms. But if untreated, it may progress and cause 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 have symptoms of vitamin B12 deficiency, you can ask your doctor for a blood test.
Infants who are born to vegan mothers and exclusively breastfed are at risk for anemia, developmental delays, weakness, and failure to thrive.
Treatment for Vitamin B12 Deficiency
If you have pernicious anemia or a problem with its absorption, you’ll need to replace vitamin B12 by injection initially and then continued injections, high doses of an oral replacement, or nasal therapy for life.
If the issue is that you don’t eat animal products, you can change your diet to include vitamin B12-fortified grains, a supplement or B12 injections, or a high-dose oral vitamin B12 if you are deficient.
The elderly should take a daily B12 supplement or a multivitamin that contains B12.
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.
University of Florida Institute of Food and Agricultural Sciences (IFAS) Extension: “Facts About Vitamin B12.”
University of Arizona’s Arizona Telemedicine Program: “Vitamin B12 Deficiency: Pernicious Anemia.”
Harvard Health Publications: “Vitamin B12 Deficiency: Vegetarians, elderly may not get enough vitamin B12, says the Harvard Health Letter.”
National Heart, Lung, and Blood Institute: “Pernicious Anemia.”
Oregon State University’s Linus Pauling Institute: “Vitamin B12.”
Kaiser Permanente: “Vitamin B12 Deficiency Anemia.”
National Institutes of Health Office of Dietary Supplements: ” Vitamin B12.”
MedlinePlus: “Anemia — B12 deficiency.”