RBP4 levels of the patients with IFG, insulin resistance or hyperinsulinemia were significantly higher than the patients without IFG, insulin resistance or hyperinsulinemia (57.39 ± 17.34 mg/L vs. 48.52 ± 16.29 mg/L, P = 0.035; 55.18 ± 16.90 mg/L vs. 39.57 ± 12.45 mg/L, P = 0.001; 55.58 ± 17.81 mg/L vs. 44.33 ± 13.67 mg/L, P = 0.007). Here, RBP4 is linked to hyperinsulinism.