Introduction: Second-generation basal insulins like glargine 300 U/mL (Gla-300) have a longer duration of action and less daily fluctuation and interday variability than first-generation ones, such as glargine 100 U/mL (Gla-100). The EF-BI study, a nationwide observational, retrospective study, was designed to compare persistence, acute care complications, and healthcare costs associated with the initiation of such basal insulins (BI) in a real-life setting in France. Methods: This study was conducted using the French healthcare claims database (SNDS). Adult patients living with type 1 or type 2 diabetes mellitus (T1DM or T2DM) initiating Gla-300 or Gla-100 ± other hypoglycemic medications between January 1, 2016 and December 31, 2020, and without any insulin therapy over the previous 6 months were included. Persistence was defined as remaining on the same insulin therapy until discontinuation defined by a 6 month period without insulin reimbursement. Hospitalized acute complications were identified using ICD-10 codes. Total collective costs were established for patients treated continuously with each basal insulin over 1-3 years. All comparisons were adjusted using a propensity score based on initial patient/treatment characteristics. Results: A total of 235,894 patients with T2DM and 6672 patients with T1DM were included. Patients treated with Gla-300 were 83% (T1DM) and 44% (T2DM) less likely to discontinue their treatment than those treated with Gla-100 after 24 months (p < 0.0001). The annual incidence of acute hospitalized events in patients with T2DM treated with Gla-300 was 12% lower than with Gla-100 (p < 0.0001) but similar in patients with T1DM. Comparison of overall costs showed moderate but statistically significant differences in favor of Gla-300 versus Gla-100 for all patients over the first year, and in T2DM only over a 3-year follow-up. Conclusion: Use of Gla-300 resulted in a better persistence, less acute hospitalized events at least in T2DM, and reduced healthcare expenditure. These real-life results confirmed the potential interest of using Gla-300 rather than Gla-100.