Amadori-glycated phosphatidylethanolamine (Amadori-PE), a nonenzymatically glycated lipid formed under hyperglycemic conditions, is known as a reliable indicator of lipid glycation in vivo. We have quantified the Amadori-PE concentration in human plasma samples using a reverse-phase liquid chromatography-tandem mass spectrometry with neutral loss scan or multiple reaction monitoring. Amounts of Amadori-PE in plasma of diabetic patients (0.15 mol% of PE), diabetic patients with chronic hemodialysis (0.29 mol% of PE), and nondiabetic patients with chronic hemodialysis (0.13 mol% of PE) are higher than that of the control group (0.08 mol% of PE). In addition, the concentration of Amadori-PE was proportional to that of phosphatidylcholine hydroperoxide, a reliable indicator of membrane lipid peroxidation, in human plasma (P < 0.05). These results indicate that plasma Amadori-PE-glycated lipid product formed under hyperglycemic conditions is an inducer of membrane lipid peroxidation, and therefore lipid glycation plays an active part in the development of human disease.