Vitamin B12 Deficiency

Vitamin B12 occurs naturally in animal-derived foods and is added to some fortified foods. People who consume little or no animal-derived food can have increased risk of inadequate B12 intake unless they obtain sufficient B12 from fortified foods or supplements.

• Dietary intake is only one cause of B12 deficiency.
• Deficiency can result from impaired absorption, pernicious anemia, gastrointestinal disorders or surgery, and medication-related factors.
• Do not assume increasing B12-containing foods corrects deficiency caused by malabsorption.
• Do not diagnose B12 deficiency from diet history alone.

Adequate intake supports prevention of dietary inadequacy, but treatment of established deficiency depends on cause and severity.

• Source 1: https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/

Established vitamin B12 deficiency can require supplementation rather than food changes alone. Evidence indicates high-dose oral B12 can achieve hematologic and neurologic responses comparable to intramuscular B12 in some deficient patients, but treatment route and dose depend on the cause and clinical circumstances.

• Do not provide individualized supplement dosing.
• Do not assume oral therapy is appropriate for every cause or severity of deficiency.
• Neurologic symptoms or significant deficiency warrant clinical evaluation.
• Food-based strategies should not be represented as sufficient for pernicious anemia or significant malabsorption.
• Do not claim B12 supplementation provides benefit beyond correcting deficiency without separate evidence.

Correction of deficiency is clinically important, but treatment must be appropriate to the underlying cause.

• Source 1: https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
• Source 2: https://pubmed.ncbi.nlm.nih.gov/16585128/