INS and type 2 diabetes mellitus: Stage 2 is equivalent to impaired glucose tolerance (IGT) or IFG, which is stable because of maintenance of meaningful insulin secretion, such that only about 5% of individuals with IGT progress to T2D per year.58 Stage 3 is an unstable phase in which increasing glucotoxicity produces more β cell dysfunction and insulin resistance, leading to a rapid rise in glucose levels to stage 4, with more serious hyperglycemia in the range of 9–17 mM (160–300 mg/dL).