Overview of vitamin B₁₂ supplementation in adults

See Clinical aspects of key water-soluble vitamins for the physiological function of vitamin B₁₂, and the effects of and risk factors for vitamin B₁₂ deficiency. Vitamin B₁₂ is continually secreted and reabsorbed in the gastrointestinal tract, so pure dietary deficiency is rare (usually only seen in strict vegans).

Vitamin B₁₂ blood concentration should be measured regularly (eg every 1 to 2 years) in patients with risk factors for vitamin B₁₂ deficiency. If supplementation is required, vitamin B₁₂ blood concentration should be rechecked 3 to 6 months after initial supplementation. The dosage and route of supplementation should be adjusted according to response.