RBP4 and type 2 diabetes mellitus: For instance, it has been reported that the detection range of RBP4 in normal individuals is 23.0–24.3 μg/mL (1–1.06 μM) and ranges from 24.9–50.3 μg/mL (1.08–2.187 μM) in individuals who are diagnosed with T2DM [22].