GPT and cholestasis: Thus, Hy’s law is used to predict severe DILI by measuring (1) hepatocellular injury by three-fold greater elevation above the upper limit normal (ULN) in alanine aminotransferase (ALT) or aspartate aminotransferase (AST), (2) the elevation of total bilirubin levels two-fold above the ULN without initial indication of cholestasis, and (3) no other reason for the elevation in transaminases or bilirubin levels.