Vitamin B12

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How does Vitamin B12 work?

Vitamin B12 is required for the proper function and development of the brain, nerves, blood cells, and many other parts of the body.

Are there safety concerns?

Vitamin B12 is safe for most people when taken by mouth or when the prescription-only, injectable product is used correctly. In some people, vitamin B12 might cause diarrhea, blood clots, itching, serious allergic reactions, and other side effects.

Vitamin B12 is likely safe for pregnant or breast-feeding women when taken by mouth in the amounts recommended. The recommended amount for pregnant women is 2.6 mcg per day. Breast-feeding women should take no more than 2.8 mcg per day.

Vitamin B12 also appears to be safe when used on the skin for psoriasis. Mild itching has been reported in one person who used a specific avocado oil plus vitamin B12 cream for psoriasis.

Do not take vitamin B12 if:
  • You have high numbers of red blood cells (polycythemia vera) or abnormal red blood cells (megaloblastic anemia).
  • You have Leber's disease, a hereditary eye disease.
  • You are allergic or sensitive to cobalt or cobalamin.

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Report Problems to the Food and Drug Administration

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.


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