Serum AST stands for aspartate aminotransferase and is highest in the myocardium and second highest in the liver. When there is damage to the liver, there is an increase in AST, for example, in acute viral hepatitis, there is a significant increase in AST. AST also increases in chronic hepatitis and fatty liver. In cirrhosis and hepatocellular carcinoma, AST will be mildly elevated. In other diseases, such as infectious mononucleosis, serum AST is also elevated. Checking the AST requires a blood test in the morning.