Last reviewed: November 2017
Last updated: November  2017



History and exam

Key diagnostic factors

  • presence of risk factors
  • old age
  • hx of gastric surgery, gastrectomy, or bypass for obesity

Other diagnostic factors

  • paraesthesias
  • vegan and vegetarian diet
  • chronic GI illnesses (e.g., Crohn's disease or coeliac disease)
  • medicine (proton-pump inhibitors, H2 receptor antagonists, metformin, anticonvulsants)
  • ataxia
  • decreased vibration sense
  • positive Romberg's test
  • pallor
  • petechiae
  • glossitis
  • angular cheilitis
  • cognitive impairment

Risk factors

  • age >65 years
  • gastric surgery (bypass or resection)
  • terminal ileum disease
  • vegan diet
  • metformin use
  • H2 receptor antagonist or proton-pump inhibitor use
  • Helicobacter pylori infection
  • anticonvulsant use
  • diabetes mellitus
  • pregnancy

Diagnostic investigations

1st investigations to order

  • serum vitamin B12
  • FBC
  • peripheral blood smear
  • reticulocyte count
Full details

Investigations to consider

  • methylmalonic acid (MMA)
  • homocysteine
  • holotranscobalamin
  • intrinsic factor (IF) antibody
  • antiparietal cell (APC) antibody
  • serum gastrin (fasting)
  • Schilling test
Full details

Treatment algorithm


Authors VIEW ALL

Robert C. Oh

Chief Medical Officer

Martin Army Community Hospital

Fort Benning



RCO declares that he has no competing interests.

Peer reviewers VIEW ALL

Chief Fellow

Section of Hematology and Oncology

Department of Internal Medicine

Wake Forest University Baptist Medical Center




RC declares that she has no competing interests.

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