ObjectivesTo explore trends in pharmaceutical expenditure on diabetes between 2011 and 2015, describing trends in expenditure on blood glucose-lowering medications and estimating the effect of cost-containment measures implemented during this time.DesignRepeated cross-sectional study of national pharmacy claims data in Ireland.ParticipantsPatients’ dispensed items used in the treatment or management of diabetes.Primary and secondary outcomesTotal expenditure associated with diabetes was calculated by extracting data on all diabetes-related items dispensed to eligible patients. Costs were categorised into two groups. Diabetes-specific items include items used directly in diabetes treatment (WHO-Anatomical Therapeutic Chemical (ATC): A10, V07, V04) and diabetes-related include all other condition-related items (WHO-ATC: B01, C, H04, N03, N06). The impacts of two specific cost-containment measures, co-payments and reference pricing, were assessed using segmented linear regression analyses of interrupted time-series.ResultsTotal expenditure varied over the study period, peaking at €216 994 441 in 2012. Expenditure on diabetes-specific items increased steadily by 18% reaching €153 621 477 in 2015, with blood glucose-lowering medications accounting for 73% of this increase. During the same period, expenditure on diabetes-related items decreased by 32% to €50 835 856. The introduction of reference pricing for atorvastatin in November 2013 resulted in immediate costs savings of €2.4 million per yearly quarter (level-change p<0.001).ConclusionsThe increasing expenditure on blood glucose-lowering medications negates the effect of recent cost-containment measures, presenting a significant challenge for the provision of diabetes care. Innovative policies are required to ensure high-quality diabetes care can be provided at an equitable, affordable and sustainable rate.