Key investigations

Measure the serum paracetamol and serum alanine aminotransferase (ALT) concentrations on presentation if the patient meets the criteria for unintentional paracetamol poisoning (see Toxic dose). The serum ALT concentration is used to predict the risk of toxicity. Most patients who develop hepatotoxicity (serum ALT concentration 1000 U/L or higher) have an initial serum ALT concentration of 50 U/L or higher.

Other investigations that may be performed if the ALT concentration is abnormal include:

• blood glucose concentration
• serum electrolyte, urea and creatinine concentrations
• INR
• blood gas analysis.