Vitamin B12

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Vitamin B12
  Evaluated for:
Effectiveness Rating Effectiveness Rating
Documented B12 Deficiency
+3 (Strong Evidence)
Pernicious Anemia
+3 (Strong Evidence)
Taking Metformin (diabetes medication)
+2 (Moderate Evidence)
0 (Unclear Effectiveness)
0 (Unclear Effectiveness)


  • Vitamin B12, or cobalamin, is an essential dietary vitamin. Deficiencies affect primarily the circulatory (blood) and nervous systems. Insufficient B12 levels can cause many different symptoms, including anemia, numbness and tingling in the hands and feet, weakness, memory loss, gait disturbances, fatigue, and mood disorders, such as depression.
  • Populations at highest risk of developing a deficiency appear most commonly in older adults, strict vegetarians, and people with gut conditions like celiac or inflammatory bowel disease that interfere with absorption of nutrients. Longstanding users of metformin, a diabetes medication, and stomach-acid blockers, such as omeprazole or lansoprazole, are also at increased risk.
  • Oral B12 supplements can treat and/or prevent B12 deficiency in high-risk groups.


  • Whereas the benefits of B12 replacement are clear in people with documented deficiencies, supplementation is not likely to be helpful in people who already have adequate B12 stores.
  • Multivitamins usually include a small amount of vitamin B12, but not nearly enough for patients with a documented deficiency. In this case, the need for additional supplementation is virtually certain.
  • Vitamin B12 supplements have the potential to hide a deficiency of folate (vitamin B9) or, conversely, to unmask a disease of excess red blood cells called polycythemia vera. To confirm that the patient is responding appropriately to treatment, doctors usually order additional blood tests after a period of time on B12.

DOSAGE:1000 micrograms daily by mouth

CONCLUSION: We conclude that Vitamin B12 is a safe and effective product for treating documented B12 deficiencies and individuals at high risk due to medication. There is not enough evidence for us to recommend its use for dementia. If you use it, remember to include it in your list of medications when you visit your doctor and other health care providers.

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