Objective: We compared the clinical course of type 2 diabetic patients whose basal insulin preparations were replaced from insulin glargine (IGlar) 100 units/mL (U100) to IGlar biosimilar or IGlar 300 units/mL (U300).Methods: After propensity score matching, 34 patients whose basal insulin preparation was switched from IGlar U100 to IGlar biosimilar and 102 switched to IGlar U300 were observed for 6 months.Results: The HbA1c level and body weight did not change significantly after the replacement in the IGlar biosimilar or IGlar U300 groups. In the IGlar biosimilar group, the frequency of subjects who experienced hypoglycemia after the replacement (12%) was not different from before (12%). However, the frequency was significantly lower after the replacement (2%) than before (13%) in the IGlar U300 group. The change in the HbA1c level after the replacement showed a significant association with the HbA1c level at the baseline but not with the kind of IGlar. Hypoglycemia was frequently observed in subjects who had experienced hypoglycemia before the replacement.Conclusions: IGlar biosimilar and IGlar U300 induced similar HbA1c and body weight changes among type 2 diabetic patients. IGlar biosimilar is a suitable option for patients with a low risk for hypoglycemia.