OBJECTIVES: Type 2 diabetes is a difficult disease to manage and treatment is often suboptimal for many patients, in particular with insulin therapy. Prefilled insulin pens provide patients with an easier-to-manage regimen that might lead to improved adherence compared to vial/syringe use. This study analyzed the impact of switching from analog insulin in vials to the prefilled pen, FlexPen®. METHODS: Real world data from a large commercial health plan in the US were investigated and insulin daily average consumption (DACON), hypoglycemic events and health care costs were analyzed before and after switch to FlexPen®. To control for the general change in insulin consumption the FlexPen® cohort was compared to a matched cohort that continued analog insulin in vials. RESULTS: A total of 532 patients switched to FlexPen® were matched to a cohort continuing on an analog insulin (n=532) administered by vial/syringe. Insulin DACON increased in both cohorts by 6-10% from the 12-month pre-period to the 12-month post-period. However, DACON increased approximately 2 units more among patients switching to FlexPen® than the vial/syringe cohort (p=0.0299). In addition, hypoglycemic event rates decreased in the FlexPen® cohort from 6.39% in the pre-period to 4.89% in the post-period while hypoglycemic events increased in the vial/syringe cohort from 4.89% to 5.83%. Despite higher acquisition costs of FlexPen® vs. vials there were no differences in pharmaceutical costs (5,414 vs. 4,790; p=0.08) or total costs (13,214 vs. 13,211; p=0.95) in the follow-up period. CONCLUSIONS: Patients switched to FlexPen® administration experienced an increase in DACON compared to the analog vial cohort, which is likely to be associated with improved adherence. Despite increase in DACON with FlexPen®, total health care and pharmaceutical costs were similar between groups in the follow-up period. Hypoglycemic events decreased in the FlexPen® cohort while they increased in the analog vial cohort.