The present invention is directed to diagnosing, determining, and/or monitoring type 2 diabetes, pre-diabetes, insulin resistance, and their related conditions by detecting levels and modulations of Serum amyloid A protein (SAA), SAA variants and/or the phenotypic ratio of SAA. The present invention is also directed to methods for identifying and evaluating therapeutic treatments for type 2 diabetes, pre-diabetes, insulin resistance, and their related conditions by monitoring SAA, SAA variants, and/or the phenotypic ration of SAA.
