When viewing this topic in a different language, you may notice some differences in the way the content is structured, but it still reflects the latest evidence-based guidance.

Deficiência de vitamina B12

Last reviewed: 21 Aug 2025
Last updated: 16 Jul 2025

Summary

Definition

History and exam

Key diagnostic factors

  • presença de fatores de risco
  • idade avançada
  • história de cirurgia gástrica (gastrectomia ou bypass gástrico para obesidade)
Full details

Other diagnostic factors

  • parestesias
  • dieta vegana ou vegetariana estrita
  • doenças gastrointestinais crônicas (por exemplo, doença de Crohn ou doença celíaca)
  • medicamentos (inibidores da bomba de prótons [IBPs], antagonistas do receptor H2, metformina, anticonvulsivantes)
  • ataxia
  • diminuição da sensibilidade vibratória
  • teste de Romberg positivo
  • palidez
  • petéquias
  • glossite
  • queilite angular
  • comprometimento cognitivo
Full details

Risk factors

  • idade >65 anos
  • cirurgia gástrica (bypass ou ressecção)
  • doença gastrointestinal crônica
  • dieta vegana ou vegetariana estrita
  • uso de metformina
  • Uso de antagonistas do receptor H2 ou inibidor da bomba de prótons (IBP)
  • infecção por Helicobacter pylori
  • uso de anticonvulsivante
  • uso indevido de óxido nitroso
  • diabetes mellitus
  • gestação
Full details

Diagnostic investigations

1st investigations to order

  • Hemograma completo
  • esfregaço de sangue periférico
  • vitamina B12 sérica
  • contagem de reticulócitos
Full details

Investigations to consider

  • ácido metilmalônico (AMM)
  • homocisteína
  • holotranscobalamina (hTC)
  • anticorpo anti-fator intrínseco (anti-IFAB)
  • anticorpo anticélula parietal (ACP)
  • gastrina sérica (em jejum)
Full details

Treatment algorithm

ACUTE

pacientes sintomáticos

deficiência assintomática ou limítrofe

Contributors

Authors

Robert C. Oh, MD, MPH, CAQSM
Robert C. Oh

Chief Wellbeing Officer

VA Palo Alto Health Care System

Palo Alto

CA

Divulgaciones

RCO declares that he has no competing interests.

Revisores por pares

Thein Hlaing Oo, MD, FRCP Edin, FACP

Professor of Internal Medicine

Consultant Hematologist

The University of Texas MD Anderson Cancer Center

Houston

TX

Divulgaciones

THO declares that he has no competing interests.

Rebecca Connor, MD

Chief Fellow

Section of Hematology and Oncology

Department of Internal Medicine

Wake Forest University Baptist Medical Center

Winston-Salem

NC

Divulgaciones

RC declares that she has no competing interests.

Peer reviewer acknowledgements

BMJ Best Practice topics are updated on a rolling basis in line with developments in evidence and guidance. The peer reviewers listed here have reviewed the content at least once during the history of the topic.

Disclosures

Peer reviewer affiliations and disclosures pertain to the time of the review.

Referencias

Nuestros equipos internos de evidencia y editoriales colaboran con colaboradores expertos internacionales y revisores pares para garantizar que brindemos acceso a la información más clínicamente relevante posible.

Artículos principales

Devalia V, Hamilton MS, Molloy AM; British Committee for Standards in Haematology. Guidelines for the diagnosis and treatment of cobalamin and folate disorders. Br J Haematol. 2014 Aug;166(4):496-513.Texto completo  Resumen

Snow CF. Laboratory diagnosis of vitamin B12 and folate deficiency: a guide for the primary care physician. Arch Intern Med. 1999 Jun 28;159(12):1289-98.Texto completo  Resumen

Stabler SP. Clinical practice. Vitamin B12 deficiency. N Engl J Med. 2013 Jan 10;368(2):149-60. Resumen

National Institutes of Health, Office of Dietary Supplements. Vitamin B12: fact sheet for health professionals. Mar 2024 [internet publication].Texto completo

Guidelines and Protocols Advisory Committee, British Columbia. Cobalamin (vitamin B12) and folate deficiency. Apr 2023 [internet publication].​Texto completo

Artículos de referencia

Una lista completa de las fuentes a las que se hace referencia en este tema está disponible para los usuarios con acceso a todo BMJ Best Practice.
  • Diferenciales

    • Deficiência de ácido fólico (vitamina B9)
    • Síndrome mielodisplásica (SMD)
    • Doença hepática relacionada ao álcool
    Más Diferenciales
  • Guías de práctica clínica

    • Vitamin B12: fact sheet for health professionals
    • Vitamin B12 deficiency in over 16s: diagnosis and management
    Más Guías de práctica clínica
  • Folletos para el paciente

    Deficiência de vitamina B12

    Anorexia

    Más Folletos para el paciente
  • Videos

    Venopunção e flebotomia – Vídeo de demonstração

    More videos
  • padlock-lockedLog in or subscribe to access all of BMJ Best Practice

Use of this content is subject to our disclaimer