Increasing numbers of doctors in training are taking career breaks, with burnout cited as a potential cause. This study analysed General Medical Council (GMC) national training survey data (renal medicine) to understand the impacts of changing workforce demographics on trainee outcomes and wellbeing. Increasing proportions of female, Black, Asian and minority ethnic (BAME), and international medical graduates are entering the workforce. Specialty exam pass rates have fallen and are lower for BAME and international medical graduates in renal medicine. Time to complete higher specialty training has increased for female trainees. Self-reported burnout rates for renal trainees were higher than other medical specialties and highest for male BAME trainees. Burnout was only partially mitigated by less-than-full-time working, but had no impact on progression, sick-leave or time out of training. It is important to recognise changes to the workforce and proactively plan to effectively support a more diverse group of trainees, to enable them to succeed and reduce differential attainment.