The role of the protein retinol binding protein 4 (RBP4) has always been understood to be involvement in the transport of vitamin A. However, research has demonstrated that blood levels of RBP4 is closely linked with the development of insulin resistance, which predisposes individuals to type 2 diabetes and is a major risk factor for cardiovascular disease. In addition higher levels of RBP4 were closely associated with other components of metabolic syndrome, including increased body mass index, waist-to-hip ratio, serum triglyceride levels and systolic blood pressure, as well as decreased HDL levels. Further investigations indicate that RBP4 may be a useful biomarker in identifying a predisposition to type 2 diabetes and measuring therapeutic improvement.