Laboratory findings may be useful to assess the severity of illness as well as help distinguish drug induced liver injury from other pathologies. Patterns of abnormalities can also distinguish between hepatocellular and cholestatic liver injury.

Laboratory tests and findings consistent with the diagnosis of drug induced liver injury include:

• CBC with differential: may reveal eosinophilia in hypersensitivity reactions e.g. DRESS, or lymphocytosis (with atypical lymphocytes on smear) in mononucleosis-like illnesses
• Alkaline phosphatase: will be disproportionately elevated (≥ 2 times the upper limit of normal) compared to aminotransferases in cholestatic injury
• AST / serum glutamic oxaloacetic transaminase (SGOT): will be elevated ≥ 3 times the upper limit of normal in hepatocellular injury cases, and even > 20 times the upper limit of normal in acute hepatocellular injury
• ALT / serum glutamic pyruvate transaminase (SGPT): will be elevated ≥ 3 times the upper limit of normal in hepatocellular injury cases, and even > 20 times the upper limit of normal in acute hepatocellular injury
• Albumin: will be low in chronic liver injury or cases of severe acute liver injury leading to abnormal synthetic function
• Bilirubin: may be elevated in both hepatocellular and cholestatic injury
• Prothrombin time, may be elevated due to coagulopathy from either hepatocellular or cholestatic injury
• Urinalysis to assess bilirubinuria
• Drug levels, e.g. acetaminophen serum level

The following tests are also helpful in patients presenting with autoimmune-like features:

• Antinuclear antibody
• Anti-mitochondrial antibody (AMA) to distinguish from primary biliary cirrhosis
• Anti smooth muscle antibody (ASMA) to distinguish from autoimmune hepatitis