This test is used for monitoring toxicity due to paracetamol intake. It is an anti-pyretic , analgesic medication without any major anti inflammatory activity. It is metabolized through the liver with a half life of around 4 hours. One important fact to remember is that initial damage to the liver will not reflect in changes in the liver function test so this drug level is the best way to monitor toxicity. For half-life determination , take 2 specimens 4 hours apart and not the time of each draw. Half life can then be calculated accordingly. First specimen has to be drawn no sooner than 2 hours after ingestion of paracetamol.