Last reviewed: 2 Feb 2021
Last updated: 29 Sep 2020
Summary
Definition
History and exam
Key diagnostic factors
- presence of risk factors
- old age
- history of gastric surgery (gastrectomy, or bypass for obesity)
Other diagnostic factors
- paraesthesias
- vegan and strict vegetarian diet
- chronic gastrointestinal disease (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)
- chronic gastrointestinal (GI) 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
- FBC
- peripheral blood smear
- serum vitamin B12
- reticulocyte count
Investigations to consider
- methylmalonic acid (MMA)
- homocysteine
- holotranscobalamin
- intrinsic factor (IF) antibody
- antiparietal cell (APC) antibody
- serum gastrin (fasting)
Treatment algorithm
Contributors
Authors

Director
Faculty Development Fellowship
Madigan Army Medical Center
Tacoma
WA
Disclosures
RCO declares that he has no competing interests.
Peer reviewers
Chief Fellow
Section of Hematology and Oncology
Department of Internal Medicine
Wake Forest University Baptist Medical Center
Winston-Salem
NC
Disclosures
RC declares that she has no competing interests.
Use of this content is subject to our disclaimer