Presentations with acute self harm are a worldwide problem. In developed countries drug overdose is a common form of self harm, and in the UK the most frequently involved agent is paracetamol, implicated in around one-third of presentations. Risk factors for paracetamol hepatotoxicity include starvation, eating disorders, and enzyme induction from drugs and alcohol. Treatment is based on assessment of these and time since ingestion. Antidotal therapy is with acetylcysteine. Assessment of treatment efficacy is based on measurement of liver function tests and serum creatinine. Adverse reactions to the antidote acetylcysteine are frequent, thus understanding their mechanisms and treatment is important. Treatment of patients presenting after 20 hours is aimed at preventing hepatic encephalopathy. Patients presenting with severe liver damage should be considered for referral to a specialised centre