Overview
Vitamin B-12 (cobalamin) plays an essential role in red blood cell formation, cell metabolism, nerve function and the production of DNA, the molecules inside cells that carry genetic information.
Food sources of vitamin B-12 include poultry, meat, fish and dairy products. Vitamin B-12 is also added to some foods, such as fortified breakfast cereals, and is available as an oral supplement. Vitamin B-12 injections or nasal spray might be prescribed to treat vitamin B-12 deficiency.
Vitamin B-12 deficiency is not common in the U.S. However, people who follow a vegetarian or vegan diet might be prone to deficiency because plant foods don't contain vitamin B-12. Older adults and people with digestive tract conditions that affect absorption of nutrients also are susceptible to vitamin B-12 deficiency.
Left untreated, a vitamin B-12 deficiency can lead to anemia, fatigue, muscle weakness, intestinal problems, nerve damage and mood disturbances.
The recommended daily amount of vitamin B-12 for adults is 2.4 micrograms.
Research on the use of vitamin B-12 for specific activities and conditions shows:
Most people get enough vitamin B-12 from a balanced diet. However, older adults, vegetarians, vegans and people who have conditions that affect their ability to absorb vitamin B-12 from foods might benefit from the use of oral supplements.
Vitamin B-12 supplements also are recommended for women who are pregnant or breastfeeding exclusively and follow vegetarian or vegan diets.
When taken at appropriate doses, vitamin B-12 supplements are generally considered safe. While the recommended daily amount of vitamin B-12 for adults is 2.4 micrograms, higher doses have been found to be safe. Your body absorbs only as much as it needs, and any excess passes through your urine.
High doses of vitamin B-12, such as those used to treat a deficiency, might cause:
Possible interactions include:
Your doctor might recommend changing drugs or timing doses to offset any potential interactions.
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Vitamin B-12 - Mayo Clinic
