BACKGROUND:Clinical, health, and economic outcomes in patients with type 2 diabetes may be influenced by self-management behaviors and type of pharmacotherapy. OBJECTIVE:This study examined differences in medication adherence and total health care costs among patients with type 2 diabetes who initiated or converted to insulin administration with a pen device in comparison with a vial/syringe as add-on therapy to oral antidiabetic drugs. METHODS:This study evaluated patients with type 2 diabetes who were enrolled in the North Carolina Medicaid program from September 24, 2001, to July 18, 2006. Patients receiving insulin with a vial/syringe who converted to pen therapy were compared with those who remained on vial/syringe in both unmatched comparisons (n = 560 and n = 9988, respectively) and after pair-matching (both cohorts, n = 560) with the use of propensity scores. In a second analysis, patients who initiated insulin with vial/syringe (n = 1162) were compared with a cohort that initiated insulin pen therapy (n = 168) after controlling for covariates in a multivariate regression model. All included patients had complete enrollment for at least 24 months of follow-up. Multiple linear regression models were used to predict the comparative impact on total health care costs and medication adherence for each cohort. Adjusted means were calculated to determine the group differences for each outcome. RESULTS:Diabetes-related and overall medication adherence was comparable for patients initiating insulin with a pen versus a syringe (53% vs 50% and 94% vs 94%, respectively). However, total annualized health care costs were significantly lower for patients using pen therapy than for those using a syringe ($14,857.42 vs $31,764.78, respectively; P < 0.05). Cost reductions with pen therapy were reflected in hospital costs ($1195.93 vs $4965.31, respectively; P < 0.05), diabetes-related costs ($7324.37 vs $13,762.21, respectively; P < 0.05), and outpatient costs ($7795.98 vs $13,103.51, respectively; P < 0.05). However, prescription costs of syringe were significantly lower ($535.70 vs $670.52; P < 0.05) and costs of pen were higher ($840.33 vs $0; P < 0.05) in patients who were switched from syringe to pen versus those who remained on syringe therapy. CONCLUSIONS:In a state Medicaid setting among patients with type 2 diabetes, initiating insulin therapy with a pen device was associated with comparable medication adherence and significant reductions in health care resource utilization and associated costs compared with vial/syringe insulin. Health care professionals and policy makers should consider the potential economic benefits of pen therapy when initiating insulin among Medicaid beneficiaries who fail to respond to oral antidiabetic drugs.