OBJECTIVE: To estimate the lifetime benefits and costs of intensive insulin therapy for type 2 diabetes mellitus (2DM), cost-effective analysis was carried out. METHODS: Cost-effectiveness analysis (CEA) and cost-utility analysis (CUA) were carried out to estimate the lifetime benefits and costs of intensive insulin therapy (IIT) for 2DM. A Markov model base on a randomized controlled trial (Kumamoto Study) was developed. As a comparator, conventional therapy (CV) was used. A societal viewpoint was adopted for the estimation of costs, and both direct and indirect costs were evaluated. A Monte Carlo simulation was done to evaluate a confidence interval of cost-effective or cost-utility ratio. Quality of life (utility) was measured by a time-trade off method among 2DM patients. RESULTS: At lifetime follow-up among 40 years of men, expected life years (28.7 years) for IIT were longer than those (26.5 years) for CT. On the other hand, expected costs ($106,500) for ITT were higher than those ($95,600). The incremental cost per life-year gained for IIT was $3,020 (discount rate of cost and effectiveness: 5%). The incremental cost per QALY gained was $3,270. Sensitivity analysis for age, costs, and health outcomes confirmed robustness of these results. CONCLUSION: Over lifetime, IIT for 2DM not only reduces complications, but also improves QOL and increases length of life. From a societal perspective, efficiency of IIT is considerably high.