The UK’s medical workforce is under increasing strain, and this is compounded by increasing numbers of resident doctors diverging from specialist training pathways, instead entering non-training roles, reducing clinical hours or leaving the profession or UK workforce entirely. These decisions are shaped by both individual motivations and wider structural conditions, including unsatisfactory working conditions, limited flexibility and a perceived lack of support or autonomy. While pursuing alternative career routes offers personal and professional benefits, they can also delay progression to senior clinical roles, contributing to workforce instability. There remains limited understanding of how best to support retention, particularly given the varied contexts, settings and career trajectories of resident doctors. This realist synthesis will examine how, why and in what contexts resident doctors leave the National Health Service, and what interventions might support their retention.

This realist synthesis will follow Realist And Meta-narrative Evidence Synthesis: Evolving Standards guidance and will be conducted in five iterative steps: (1) identifying existing theories to develop an initial programme theory; (2) undertaking formal and purposive searches to identify relevant UK-based literature; (3) selecting documents based on relevance and rigour; (4) extracting and coding data to support the development of explanatory insights; and (5) synthesising findings using a realist logic of analysis to develop and refine context-mechanism-outcome configurations. An advisory group will guide the review throughout. The final programme theory will inform the development of evidence-based recommendations and design principles to support resident doctor retention.

Ethical approval is not required for this synthesis of existing literature. Findings will be disseminated through academic publications, conference presentations and accessible formats, including infographics, plain English summaries and blog posts. Target audiences include resident doctors, medical educators, workforce planners and policymakers.

PROSPERO, CRD420251004453.

To develop a core outcome set (COS) to capture and measure the well-being of doctors working in the National Health Service (NHS).

An online Delphi study.

UK NHS.

Participants from four stakeholder groups: (1) those who might use the COS in research, (2) organisations that measure/capture NHS staff well-being, (3) professionals with experience managing NHS staff well-being and (4) NHS doctors were identified through authorship of relevant publications, attendee lists of doctor well-being conferences and meetings, professional bodies, participation in a previous study and recommendations from others. They were recruited via email.

A two-stage process: (1) creating a list of 43 well-being outcomes informed by a systematic review of well-being measurement instruments, a survey of UK doctors and two doctor engagement workshops and (2) an online Delphi study (with two rounds) to reach consensus. Outcomes were rated on a 9-point Likert scale; ‘consensus’ was reached when ≥75% agreed that an outcome was critical for inclusion in the COS.

52 participants completed both Delphi rounds. Seven well-being outcomes met the threshold for inclusion in the COS: general well-being, health, personal safety, job satisfaction, morale, life work balance and good clinical practice.

Use of the COS has the potential to reduce heterogeneity and standardise the capture and measurement of doctor well-being, and ensure outcomes important to all stakeholders are reported.

This study was prospectively registered with the Core Outcome Measures in Effectiveness Trial initiative at www.comet-initiative.org (Registration: 1577).