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Practice Guidelines

Vitamin B12 deficiency: NICE guideline summary

BMJ 2024; 385 doi: (Published 13 June 2024) Cite this as: BMJ 2024;385:q1019

Linked Editorial

The persistent challenge of diagnosing and treating vitamin B12 deficiency

  1. Toby Sands, technical analyst1,
  2. Aamer Jawed, technical analyst1,
  3. Emma Stevenson, principal clinical biochemist2,
  4. Maddie Smith, patient author3,
  5. Imran Jawaid, portfolio general practitioner, chair of guideline committee, clinical assessment lead and associate professor4
  6. on behalf of the Guideline Committee
    1. 1National Institute for Health and Care Excellence, Manchester, UK
    2. 2Clinical Biochemistry, Gloucestershire Hospitals NHS Foundation Trust, Gloucester, UK
    3. 3Patient author
    4. 4The University of Buckingham, Buckinghamshire, UK
    1. Correspondence to: T Sands Toby.sands{at}

    What you need to know

    • Offer an initial diagnostic test (total or active B12) for suspected deficiency to people who have at least one common symptom or sign and at least one common risk factor for the condition

    • Consider a further test to measure serum methylmalonic acid concentrations in people who have symptoms or signs of vitamin B12 deficiency and an indeterminate total or active B12 test result

    • When offering oral vitamin B12 replacement to people with vitamin B12 deficiency caused, or suspected to be caused, by malabsorption, prescribe a dosage of at least 1 mg a day

    Vitamin B12 deficiency is associated with a range of symptoms and signs, resulting in substantial variation in patient presentation. While epidemiological data are limited, cross sectional studies from the UK and US suggest a prevalence of 3% in people aged 20-39, increasing with age up to about 20% in people aged 85 and over.12 Complications of vitamin B12 deficiency include visual changes, paraesthesia, and ataxia.

    In March 2024, the National Institute for Health and Care Excellence (NICE) published new guidance on the diagnosis and management of B12 deficiency.3 This summary aims to raise awareness of the symptoms and signs, assessment, and management of vitamin B12 deficiency, with particular focus on what is most relevant to general practice and primary care. Readers are directed to the full guideline for a comprehensive review of all recommendations.


    NICE recommendations are based on systematic reviews of best available evidence and explicit consideration of cost effectiveness. When minimal evidence is available, recommendations are based on the guideline committee’s experience and its opinion of what constitutes good practice. Evidence levels for the recommendations are given in italics in square brackets.

    GRADE Working Group grades of evidence

    • High certainty—we are very confident that the true effect lies …

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