AIMS To compare the real-world effectiveness of insulin degludec (degludec) and glargine 300 units/mL (glargine U300) in insulin-naive adult patients with type 2 diabetes in routine US clinical practice. MATERIALS AND METHODS CONFIRM is a non-interventional comparative effectiveness study following US patients across the continuum of care, through electronic medical records from multiple health systems and integrated delivery networks. Propensity-score matching controlled for confounding. The primary endpoint, change in HbA1c from baseline to 180 days of follow-up, was estimated using a repeated-measure of covariance analysis with subject as random effect. Change in the rate of hypoglycaemic episodes (defined using International Classification of Diseases codes 9/10) and change in proportion of patients with hypoglycaemia were estimated using negative binomial and logistic regression, respectively. Time-to-discontinuation of the initial basal insulin/initiation with another prescribed basal insulin was analysed using a Cox Proportional Hazard model. RESULTS Data concerning 4056 patients were analysed. After matching, baseline characteristics were comparable (n = 2028 in each group). After 180 days of follow-up, degludec was associated with a larger reduction in HbA1c (estimated treatment difference, -0.27%; P = 0.03), greater reductions in change in rate (rate ratio, 0.70; P