Any type of liver cell injury can cause modest elevations in the serum aminotransferases. Levels of up to 300 IU/L are nonspecific and may be found in any type of liver disorder. Minimal ALT ele- vations in asymptomatic blood donors rarely indicate severe liver disease; studies have shown that fatty liver disease is the most likely explanation. Striking elevations—that is, aminotransferases >1000 IU/L—occur almost exclusively in disorders associated with exten- sive hepatocellular injury such as (1) viral hepatitis, (2) ischemic liver injury (prolonged hypotension or acute heart failure), or (3) toxin- or drug-induced liver injury. The pattern of the aminotransferase elevation can be helpful diag- nostically. In most acute hepatocellular disorders, the ALT is higher than or equal to the AST. Whereas the AST:ALT ratio is typically <1 in="" patients="" with="" chronic="" viral="" hepatitis="" and="" nonalcoholic="" fatty="" liver="" disease,="" a="" number="" of="" groups="" have="" noted="" that="" as="" cirrhosis="" develops,="" this="" ratio="" rises="" to="">1. An AST:ALT ratio >2:1 is suggestive, whereas a ratio >3:1 is highly suggestive, of alcoholic liver disease. The AST in alcoholic liver disease is rarely >300 IU/L, and the ALT is often normal. A low level of ALT in the serum is due to an alcohol-induced deficiency of pyridoxal phosphate.