Introduction This study compared the efficacy and safety of similar U-100 insulin glargine products, namely, Lilly insulin glargine (LY IGlar; Basaglar®) and the reference insulin glargine product (IGlar; Lantus®), used once daily in combination with oral antihyperglycemic medications (OAMs) in adults with type 2 diabetes (T2D). Methods ELEMENT 5 was a phase III, randomized, multinational, open-label, treat-to-target, 24-week trial. Participants were insulin naïve (glycated hemoglobin [HbA1c] ≥ 7.0% to ≤ 11.0%) or on basal insulin (IGlar, neutral protamine Hagedorn or insulin detemir; HbA1c ≤ 11.0%) and taking ≥ 2 OAMs. The primary objective was to show that LY IGlar is noninferior to IGlar in terms of HbA1c reduction (0.4% noninferiority margin). Results The study population (N = 493) was predominantly Asian (48%) or White (46%), with similar baseline characteristics between arms (P > 0.05). At 24 weeks, LY IGlar was noninferior to IGlar in terms of change in HbA1c level from baseline (− 1.25 vs. − 1.22%, respectively; least squares mean difference − 0.04%; 95% confidence interval − 0.22%, 0.15%). Other 24-week efficacy and safety results were also similar between treatments (P > 0.05), including insulin dose; percentage of patients having HbA1c of