OBJECTIVE: Glycemic variability may contribute to adverse medical outcomes of type 2 diabetes, but prior therapies have had limited success in controlling glycemic fluctuations, and the hypothesis has not been adequately tested. RESEARCH DESIGN AND METHODS: People with insulin-requiring type 2 diabetes and high cardiovascular risk were enrolled during a run-in period on basal-bolus insulin (BBI), and 102 were randomized to continued BBI or to basal insulin with a prandial GLP-1 receptor agonist (GLIPULIN) group, each seeking to maintain HbA(1c) levels between 6.7% and 7.3% (50-56 mmol/mol) for 6 months. The primary outcome measure was glycemic variability assessed by continuous glucose monitoring; other measures were HbA(1c), weight, circulating markers of inflammation and cardiovascular risk, albuminuria, and electrocardiographic patterns assessed by Holter monitoring. RESULTS: At randomization, the mean age of the population was 62 years, median duration of diabetes 15 years, mean BMI 34 kg/m(2), and mean HbA(1c) 7.9% (63 mmol/mol). Thirty-three percent had a prior cardiovascular event, 18% had microalbuminuria, and 3% had macroalbuminuria. At baseline, the continuous glucose monitoring coefficient of variation for glucose levels was similar in both groups. CONCLUSIONS: FLAT-SUGAR is a proof-of-concept study testing whether, in a population of individuals with type 2 diabetes and high cardiovascular risk, the GLIPULIN regimen can limit glycemic variability more effectively than BBI, reduce levels of cardiovascular risk markers, and favorably alter albuminuria and electrocardiographic patterns. We successfully randomized a population that has sufficient power to answer the primary question, address several secondary ones, and complete the protocol as designed.