Aims Improving transition from paediatric to adult healthcare is a priority for diabetes services. Guidance is that all type 1 patients should transition to adult diabetes services. Yet little is known about system-level performance for transition and no population-based studies have examined predictors of or outcomes of transition at the national level.

Methods We obtained routine hospital administrative data (Hospital Episode Statistics; HES) for England and linked ONS mortality data from 2004/5 to 2014/15, obtained for all those aged 10–18 years in 2004. We defined our diabetes (type 1 or 2) cohort as being any inpatient admission with a diabetes ICD10 code during the study period. We defined two measures of good transition. Successful transition was defined as any adult service contact within 6 months of last paediatric content. Successful retention was defined as having first planned adult contact within six months of the last planned paediatric contact, and at least two further adult contacts within the next two years. We used multilevel models in Stata to examine demographic and health service predictors and outcomes of successful transition.

Results 8793 individuals were identified with diabetes, with a total of 3 30 019 care episodes. 15.2% had no post-paediatric adult episodes. 47.9% transitioned within 6 months and 41.9% transitioned and were retained in adult services for the subsequent two years.

Poor transition (6m) and poor retention were significantly predicted by deprivation, male sex, <2 outpatient appointments in year before transfer, and younger age at transfer, but not ethnicity. Provider level variation was high – 12% for successful transition and retention and 30% for age at transition.

Transition within 6 months and successful retention predicted lower post-transition emergency health service use (e.g. admissions and A and E use; p<0.001). Transitioning within 6 months also predicted a lower risk of mortality (OR: .74; 95% CIs: .56, .99)

Conclusion Overall system performance for diabetes transition is mixed in England. There is unacceptable provider level and regional variations in transition outcomes. We provide the first population-evidence that good transitions reduce later emergency health service use and mortality