Vitamin B12

Is Vitamin B12 Effective?

As you might expect, this vitamin is effective for treating vitamin B12 deficiencies. It may also be useful for treating hyperhomocysteinemia. There is not enough evidence to suggest that it works for most other uses.
(Click Does Vitamin B12 Work? for more information.)

Dosing Information

Because it has been studied quite a bit, good information about vitamin B12 dosing is available. For some of the less studied uses, the most effective (and safe) doses have not yet been established. Recommended Dietary Allowances (RDAs) have been established for the vitamin.
(Click Vitamin B12 Dosage for more information.)

Side Effects of Vitamin B12

Most people do not experience side effects, even with high doses. However, a few possible side effects have been reported in clinical studies. Some side effects of vitamin B12 may include:
  • Diarrhea
  • Rash
  • Itching
  • Blood clots in the legs.
(Click Vitamin B12 Toxicity to learn more, including potentially serious side effects you should report immediately to your healthcare provider.)

Drug Interactions

Vitamin B12 can potentially interact with a few medications (see Vitamin B12 Drug Interactions).
Last reviewed by: Kristi Monson, PharmD
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