This guideline covers recognising, diagnosing and managing vitamin B12 deficiency in people aged 16 and over, including deficiency caused by autoimmune gastritis. It also covers monitoring for gastric cancer in people with autoimmune gastritis.

Last reviewed: 6 March 2024

Next review: This guideline will be reviewed if there is new evidence that is likely to change the recommendations.

In this guideline, we do not use the term pernicious anaemia to describe autoimmune gastritis. See the definition of autoimmune gastritis in the terms used in this guideline for more details.


This guideline includes recommendations on:

See the 2-page visual summary on ongoing care and follow-up options for oral and intramuscular vitamin B12 replacement.

View visual summary

Who is it for?

  • Health and social care professionals providing NHS-commissioned services
  • Commissioners of services
  • Laboratories
  • People with confirmed or suspected vitamin B12 deficiency, their families and carers

Guideline development process

How we develop NICE guidelines

Your responsibility

The recommendations in this guideline represent the view of NICE, arrived at after careful consideration of the evidence available. When exercising their judgement, professionals and practitioners are expected to take this guideline fully into account, alongside the individual needs, preferences and values of their patients or the people using their service. It is not mandatory to apply the recommendations, and the guideline does not override the responsibility to make decisions appropriate to the circumstances of the individual, in consultation with them and their families and carers or guardian.

All problems (adverse events) related to a medicine or medical device used for treatment or in a procedure should be reported to the Medicines and Healthcare products Regulatory Agency using the Yellow Card Scheme.

Local commissioners and providers of healthcare have a responsibility to enable the guideline to be applied when individual professionals and people using services wish to use it. They should do so in the context of local and national priorities for funding and developing services, and in light of their duties to have due regard to the need to eliminate unlawful discrimination, to advance equality of opportunity and to reduce health inequalities. Nothing in this guideline should be interpreted in a way that would be inconsistent with complying with those duties.

Commissioners and providers have a responsibility to promote an environmentally sustainable health and care system and should assess and reduce the environmental impact of implementing NICE recommendations wherever possible.