OBJECTIVES: Previous research suggests elderly patients with type-2 diabetes mellitus (T2DM) are likely discharged without anti-hyperglycemic medication after an admission for myocardial infarction (MI). Our study aimed to evaluate anti-hyperglycemic medication use post-MI in a commercially insured population. METHODS: We assembled a nation-wide population-based cohort of patients with T2DM continuously enrolled by a private insurer between January 2007 and December 2009. T2DM was defined based on diagnosis codes (Chronic Condition Data Warehouse definition) and pharmacy claims for an anti-hyperglycemic drug. We identified patients who experienced MI (ICD-9 code 410.xx) during our study period and evaluated anti-hyperglycemic treatment before and after the cardiac event. We described medication utilization and investigated changes in medication use from pre- to post-MI. Logistic regression and resulting odds ratios (OR) with associated 95% confidence intervals (CI) were used to evaluate factors predicting treatment post-MI.  RESULTS: We identified 25,136 diabetic patients that experienced MI. Prior to MI, over 30% of the patients had a prescription for an anti-hyperglycemic drug, with approximately 12% receiving multiple drug regimens. The majority of the patients were treated with metformin (42%), followed by a sulfonylurea agent. Post-MI, 34% were treated; of the 75% with a prescription within 30 days, 35% received metformin. The median time from discharge until the first prescription fill was 25 days (interquartile range= 62). About 29% of those treated pre-MI, did not receive medication post-MI; about 1 in 8 patients initiated anti-hyperglycemic medication within 30 days post-MI. Demographic characteristics and pre-MI treatment predicted treatment after MI. Older patients were less likely to fill a prescription post-MI (adjusted OR=0.974; 95% CI: 0.972-0.977).  CONCLUSIONS: Many T2DM patients experiencing an MI are not discharged on previously prescribed anti-hyperglycemic medications. Assessment of short and long-term outcomes in patients not receiving anti-hyperglycemic medications post-MI, particularly in the elderly, warrants further investigation.