OBJECTIVES To examine the association between nonadherence to oral hypoglycemics and potentially avoidable hospitalizations due to diabetes short-term complications among Medicare Part D enrollees. METHODS This is a longitudinal retrospective cohort study. Medicare Part D enrollees with diabetes from six states (Alabama, California, Florida, Mississippi, New York, and Ohio) who had filled at least 1 prescription for oral hypoglycemics during the first half of 2006 were included in the study. Medicare Part D claims data for the first 6 months of 2006 were evaluated for adherence with oral hypoglycemics using proportion of days covered (PDC). Patients were classified as adherent (PDC ≥0.8), poor adherent (0.5≤ PDC <0.8), and very poor adherent (0RESULTS Data were available for 1,101,533 patients. Among them, 58.4% were females and the mean age was 71.7 years. About 64.9% were adherent, 11.2% were poor adherent, and 24.0% were very poor adherent with oral hypoglycemics. Of all patients, 1540 had at least one hospital admissions due to diabetes short-term complications during the outcome measurement period. After controlling for age, gender, race, and comorbidities (Charlson Comorbidity Index), the odds for hospital admission due to diabetes short-term complications was 25.4% (OR: 1.254; 95%CI: 1.072-1.467) higher for poor adherent patients and 48.0% (OR: 1.480; 95%CI: 1.326-1.653) higher for very poor adherent patients when compared to patients who were adherent to oral hypoglycemics. CONCLUSIONS Nonadherence to oral hypoglycemics is associated with increased risks for potentially avoidable hospitalizations due to diabetes short-term complications. Medicare prescription drug plans should consider developing targeted interventions to improve adherence to oral hypoglycemics.