Disclosed are a composition and method for the diagnosis of diseases accompanied by impaired glucose tolerance, comprising a material for ITIH1 detection. The composition and method according to the present application enable a relatively sensitive response even to small changes in blood sugar according to various stimulants in a hyperglycemic situation as compared to glycated hemoglobin (HbA1c) which is an existing diagnostic marker widely used for patients with diabetes, which is a typical disease accompanied by impaired glucose tolerance, and thus can more precisely detect blood sugar changes under various stress situations.