BACKGROUND:  As age increases, prevalence of type 2 diabetes in the U.S. rises dramatically as the population approaches and enters Medicare eligibility (CDC). Although ensuring category access, CMS formulary guidelines for Medicare Part D (MPD) coverage do not take into account the effects of cost-sharing burden on patient compliance.  Literature demonstrates that patient adherence is reduced with higher copayment costs and consequently, the beneficial clinical impacts may likely be unrealized for many patients. OBJECTIVES: To investigate access to diabetic medications for MPD patients compared to commercially covered lives. Exploring copay differentials amongst these populations, insight is gained on how MPD differs from commercial access to diabetes medications. METHODS: Analysis of the Walters Kluwer Pharma Solutions Source Longitudinal Patient Database, sampling of 26.7 million commercial lives and 5 million Medicare Part D lives in 2009. Low Income Subsidy covered lives were excluded. RESULTS: Average drug copayment for metformin and sulfonylurea for commercial and MPD patients is $15 and $19 respectively.  Average drug copayment for insulin glargine in commercial is $17 and $27 for MPD patients, for branded pioglitazone $31 and $52, and exenatide $32 and $68.  CONCLUSIONS: Copayment differentials across these populations are small for generic therapies and grow larger for branded, novel diabetic agents.   This data would suggest a broader, more inclusive review is needed to assess how the financial burden felt by MPD diabetes patients affects patient compliance and outcomes.  Further investigation is needed to study the potential value that CMS would benefit from re-evaluating the cost sharing burden for this patient population