OBJECTIVES: The study aims to assess the cost-utility of insulin glargine 300U/ml (GLA-300) compared to a biosimilar of insulin glargine 100U/ml (GLA-100) and insulin degludec 100U/ml (DEG-100) in patients with type 2 diabetes mellitus in Slovenia. METHODS: A cost-utility model was developed to estimate differences in costs and clinical outcomes. The perspective of the analysis was that of a healthcare payer in Slovenia within one year time horizon. Main outcome was incremental cost-effectiveness ratio (ICER) expressed in Euros (EUR) per quality adjusted life years (QALYs). Costs considered were drug costs, resource consumption costs and costs of treating hypoglycaemia. Insulin dosages used per each of the comparators relied on pooled analysis of EDITION 1-2-3 clinical trials. Efficacy in the model was analysed based on comparators’ impact on: incidence of hypoglycaemic events, body mass index and dosage flexibility. Changes of these parameters were cited from EDITION 1-2-3 for comparison with GLA-100, and from network meta-analysis for comparison with DEG-100. Probabilistic sensitivity analysis (PSA) was conducted to test the model robustness. RESULTS: In the base case analysis, GLA-300 was associated with incremental QALYs compared to GLA-100 and DEG-100 estimated at 0.0082 and 0.0112, respectively. Total costs associated with GLA-300 were higher than those of GLA-100 (+€171.7) and lower than those of DEG-100 (-€624.4). In comparison with GLA-100, the estimated ICER was €20,911/QALY, while in comparison with DEG-100, GLA-300 was pharmacoeconomically dominant as it obtains additional health gains with associated cost savings. At the €25,000 cost-effectiveness threshold, PSA estimated a probability of 54% and 99% for GLA-300 being cost-effective in comparison with GLA-100 and DEG-100, respectively. CONCLUSIONS: Based on a reduced incidence of hypoglycaemia and possibility for dose flexibility, GLA-300 is likely to be cost effective in economic and clinical conditions of Slovenia in comparison to GLA-100 and pharmacoeconomically dominant in comparison to DEG-100.