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Vitamin B12 deficiency

Guidelines

Key sources

The following summarized guidelines for the evaluation and management of vitamin B12 deficiency are prepared by our editorial team based on guidelines from the American Diabetes Association (ADA 2025), the European Association of Urology (EAU 2025), the European Association for the Study of the Liver (EASL 2022), the Italian Society of Digestive Endoscopy (SIDE/SIGE 2022), the American Society of Anesthesiologists ...
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Screening and diagnosis

Indications for screening, general principles: as per AAFP 2017 guidelines, obtain screening with a CBC and serum vitamin B12 level measurement in patients with risk factors for vitamin B12 deficiency.
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  • Indications for screening (elderly patients)

  • Indications for screening (vegetarians)

  • Indications for screening (patients on metformin)

  • Indications for screening (IBD)

  • Indications for screening (CKD)

  • Indications for screening (polyneuropathy)

  • Indications for screening (pre-bariatric surgery)

  • Indications for screening (post-bariatric surgery)

  • Indications for screening (post-radical cystectomy)

  • Indications for screening (primary adrenal insufficiency)

  • Indications for screening (hematological disorders)

  • Diagnostic criteria

Diagnostic investigations

Serum vitamin B12 and folate: as per BSH 2014 guidelines, assess serum vitamin B12 and folate levels in patients with suspected vitamin B12 deficiency.
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  • Serum homocysteine and MMA

  • Serum holotranscobalamin

  • Evaluation for pernicious anemia

  • Screening for H. pylori infection

  • Screening for gastric cancer

Medical management

Vitamin B12 supplementation, without neurological involvement: as per AAFP 2017 guidelines, administer oral or injectable preparations for vitamin B12 replacement recognizing that injectable therapy leads to more rapid improvement. Consider administering injectable vitamin B12 preparations in patients with severe vitamin B12 deficiency.
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  • Vitamin B12 supplementation (with neurological involvement)

Specific circumstances

Pediatric patients: as per BSH 2014 guidelines, treat vitamin B12 deficiency promptly in infants to prevent long-term neurological sequelae.
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  • Pregnant patients

  • Patients on metformin

  • Patients on hormone therapy

  • Patients with pernicious anemia

  • Patients with chronic liver disease

  • Patients with food-bound cobalamin malabsorption

Preventative measures

Prophylactic vitamin B12 supplementation, post-bariatric surgery: as per AAFP 2017 guidelines, initiate oral vitamin B12 supplementation (1 mg/day) and continue indefinitely in patients post-bariatric surgery.
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  • Prophylactic vitamin B12 supplementation (patients on pemetrexed)

  • Prophylactic vitamin B12 supplementation (patients on metformin)

  • Prophylactic vitamin B12 supplementation (CVD)

  • Prophylactic vitamin B12 supplementation (PAD)

  • Prophylactic vitamin B12 supplementation (atopic dermatitis)

  • Prophylactic vitamin B12 supplementation (sleep-wake disorder)