Clinician awareness and implementation of MHRA guidance on vitamin B12 monitoring in metformin users: a reflexive thematic analysis of primary care practice

Abstract Background Metformin is the first line pharmacological treatment for type 2 diabetes mellitus (T2DM) but is associated with vitamin B 12 deficiency. In 2022, the Medicines and Healthcare products Regulatory Agency (MHRA) issued a Drug Safety Update recommending testing in symptomatic patients and consideration of periodic monitoring in those at risk. Earlier quantitative research identified only a modest increase in recorded testing and high clinician awareness alongside inconsistent monitoring. Therefore, this study aimed to explore clinician awareness of the MHRA update and examine how guidance on vitamin B 12 monitoring was interpreted and implemented within primary care. Methods A qualitative study using semi-structured interviews was conducted with clinicians involved in diabetes care within general practice in the South-West of England. Participants were recruited from respondents to a preceding survey who had expressed an interest in follow-up interviews. The interviews were conducted remotely between October 2025 and January 2026 and transcribed verbatim, with the data analysed using reflexive thematic analysis. Results Eighteen clinicians participated, including general practitioners, nurses and pharmacy professionals. Four themes were developed: preventive monitoring under service pressure, navigating roles and responsibility in diabetes care, translating guidance into practice, and pragmatic decision-making under uncertainty. Monitoring was described more consistently where vitamin B 12 testing had been included within an existing diabetes care process. However, where no process had been established, testing remained dependent on the clinician identifying the need, interpreting the guidance and deciding who was responsible for acting. Conclusions The findings show that variation in vitamin B 12 monitoring was not explained by clinician awareness alone, as the MHRA alert communicated the risk without establishing how monitoring should be organised within primary care. Where testing had not been incorporated into an existing diabetes care process, the frequency of monitoring and professional responsibility remained uncertain. Improving implementation may therefore require an agreed process through which monitoring can be included within routine diabetes care, although further evaluation is required to determine which approach would be effective.