Insulin is increasingly being used in the treatment of type 2 diabetes. Insulin is beneficial in enhancing glycemic control and thus reducing microvascular risk, but the safety of its long-term application is raising concerns. Recent studies have shown that insulin increases the incidence of all-cause mortality, major adverse cardiovascular events (MACE), malignancy, and other adverse outcomes in patients with type 2 diabetes compared with other glucose-lowering regimens. However, the dose of insulin used was not explored in the aforementioned studies. To this end, Holden et al. from Cardiff University School of Medicine, UK, conducted a retrospective study to assess the relationship between insulin dose and the incidence of all-cause mortality, MACE and malignancy. The findings were published online in the December 10, 2014 issue of Diabetes Obesity andMetabolism. Researchers collected information on 6,484 patients with type 2 diabetes from the Clinical Practice Research Datalink (CPRD) in the United Kingdom who first started insulin monotherapy after Jan. 1, 2000. The researchers estimated the patients’ insulin use (international units/kg/d) from their prescriptions and body weight, and then compared the risk of serious adverse events using a Cox proportional risk model. The primary endpoints of the study included all-cause death, MACE (including myocardial infarction, stroke, or cardiovascular death), and malignancy. Researchers followed patients at the time they first received insulin monotherapy for a mean follow-up of 3.3 years. The results showed that the number of all-cause deaths, MACE, and malignancies were 1110, 342, and 382, respectively; the uncorrected rates of these events were 61.3, 26.4, and 24.6 per 1000 patient-years, respectively; and the corrected hazard ratios (HRs) for a 1 unit/kg/d increase in insulin dosage were 1.54, 1.5, and 1.5, respectively. The results of this study suggest that insulin dosage is associated with the risk of all-cause mortality, MACE and malignancy in patients with type 2 diabetes when treated with insulin monotherapy. However, the nature of the retrospective study and the estimation of insulin dose made the study limited, so interventional studies are needed to validate this result. Currently, further studies should be conducted to explore the risks and benefits of insulin use in patients with type 2 diabetes.