The UK’s National Health Service (NHS) faces a persistent workforce crisis, with doctor shortages exacerbated by high attrition and outward migration of UK-trained doctors. Despite extensive public subsidy of medical training—estimated at £250 000 per doctor to the point of full General Medical Council registration—there is currently no requirement for UK-trained doctors to serve a minimum number of years in the NHS. Many UK-trained doctors leave the NHS early in their career, often to practise overseas in healthcare systems that did not contribute to their training. This paper makes the case for introducing a minimum NHS service requirement for UK-trained doctors—advancing a policy proposal grounded in ethical principles—akin to obligations already established in the British Armed Forces for sponsored medical students. The analysis highlights the significant financial burden of training and replacing doctors, estimated at £350 000 per individual lost after 1 year of NHS service, as well as non-financial costs including lost expertise, disrupted continuity of care and opportunity costs arising from oversubscribed medical school places. A minimum service requirement could mitigate these inefficiencies by ensuring a greater return on public investment and encouraging self-selection among applicants more committed to long-term NHS service. Potential objections—including concerns about fairness, autonomy, unintended attrition at later stages and recruitment impacts—are considered and addressed. While further empirical research is needed to refine the optimal duration and assess behavioural impacts, the introduction of a minimum NHS service requirement represents a pragmatic strategy to strengthen workforce retention and protect taxpayer investment.