Do clinical features differ between people with prediabetes?

    Written by:
    Mike Murray

    Fact-checked

    by:

    Louie Neri, Graham Walker
    Last Updated: May 16, 2025

    Clinical features of prediabetes differ between people with impaired fasting glucose (IFG) and people with impaired glucose tolerance (IGT), primarily in the sites of insulin resistance and insulin secretion responses. IFG is characterized by insulin resistance in the liver with an impaired early-phase insulin response, whereas IGT is characterized by severe insulin resistance in skeletal muscle and an impaired late-phase insulin response.

    Prediabetes can be diagnosed using either fasting plasma glucose, 2-hour plasma glucose during an oral glucose tolerance test (OGTT), or HbA1c. The clinical features displayed by people with impaired fasting glucose (IFG) differ from those with impaired glucose tolerance (IGT) or elevated 2-hour plasma glucose levels during an OGTT.

    Both are characterized by insulin resistance, but differ in the primary site of insulin resistance. In IFG, there is insulin resistance in the liver and normal insulin resistance in skeletal muscle, whereas IGT exhibits little to no insulin resistance in the liver and severe insulin resistance in skeletal muscle.[1] There are also differences in insulin secretion. In response to oral glucose, people with IFG have an impaired early-phase (first 30 minutes) insulin response, whereas people with IGT have an impaired late-phase insulin response.[2] During an OGTT, people with IFG exhibit higher plasma glucose levels than people with IGT at 30–60 minutes. Plasma glucose levels then return to around baseline at 120 minutes, while they remain significantly elevated in people with IGT.[2]