The Affordable Care Act created provisions to expand Medicaid coverage to all individuals with incomes at or below 138 percent of the poverty line ($16,243 for an individual and $33,465 for a family of four in 2015). However, nearly three million low-income individuals in 19 states across the nation remain without health insurance following the Supreme court decision that yielded Medicaid expansion non-compulsory for states. Several studies have determined that states the that have adopted the expansion have had largely positive impacts on coverage, access to care and utilization, as well as economic outcomes. No study to date, however, has investigated the impact of Medicaid expansion on adherence to oral hypoglycemic medications. This investigation is crucial because adherence to diabetic medications can in many cases postpone or prevent the damaging and costly complications associated with the progression of diabetes. Medicaid provides access to essential medical services and prescription drugs for millions of low-income individuals, many of whom would not have health insurance otherwise and whom experience diabetes associated complications at a higher rate. This study will evaluate pharmacy claims from the Medical Expenditure Panel Survey to determine whether Medicaid expansion has, in fact, had an effect on adherence to oral hypoglycemic diabetic medications for low-income individuals. The analysis will compare pre-expansion (2013) and post-expansion (2015) adherence estimates among Medicaid expansion and non-Medicaid expansion states utilizing the difference-in-differences statistical model