BACKGROUND: Patients with T2DM tend to have long-term macrovascular complications, like acute coronary syndrome (ACS). Secondary prevention with antiplatelet medicines (aspirin, clopidogrel, prasugrel, ticagrelor) is recommended. However, evidence suggests suboptimal adherence to medicines in this patient group. The full benefits of pharmacotherapy can be attenuated if patients don’t take medications as prescribed. OBJECTIVES: To investigate adherence to antiplatelet medications prescribed in adults with T2DM for secondary prevention following ACS. METHODS: Retrospective, observational study using the UK Clinical Practice Research Datalink. Prescription records from the first prescription post-ACS event till the end of follow-up were used. (Prot.No: 16_188R2). Adherence was observed for several exposure groups (aspirin only, clopidogrel only, aspirin-clopidogrel, aspirin-prasugrel, aspirin-ticagrelor) over various time intervals (from 30 to 1440 days post-ACS,between January 2007 and December 2015). Proportion of Days Covered (PDC) was the adherence measure, and a PDC value of 80% was adopted to classify patients as “adherent”. RESULTS: Records for 21936 patients were obtained. Patients on antiplatelet monotherapy regimens followed similar adherence patterns, with PDC close to 90% until around 630 days from initiation, and then dropping, but remaining above 80% afterwards. Patients on dual antiplatelet therapy (DAPT) regimens were adherent for 12 months, with PDC dropping below 80% after 450 days in the aspirin-clopidogrel group and below 90% in the other two DAPT groups. Regimen adherence to all three DAPTs appeared to become similar after 630 days,at 65%. CONCLUSIONS: The study found good overall adherence to antiplatelet regimens in adults with T2DM. Adherence drop on DAPT regimens could be attributed to the fact that some patients might not need dual therapy for more than 12 months, and some time is needed to coordinate the switch from DAPT to antiplatelet monotherapy. Further investigation is needed to identify factors that affect antiplatelet adherence in this patient group.