The plasma concentration of xanthine showed significant positive correlations with the BMI (R = 0.39, P < 0.001), waist circumference (R = 0.42, P = 0.001), fasting IRI (R = 0.35, P = 0.001), fasting C-peptide (R = 0.32, P < 0.01), HOMA-IR (R = 0.27, P < 0.01), AST (R = 0.62, P < 0.001), ALT (R = 0.56, P < 0.001), γ-GTP (R = 0.54, P < 0.001), and Fib4-index (R = 0.43, P < 0.01), and a negative correlation with the HDL-C (R = − 0.21, P < 0.05) in patients with type 2 diabetes. Here, GPT is linked to type 2 diabetes mellitus.