Delirium is a complex clinical syndrome characterised by disturbed consciousness, cognitive function, or perception. Sometimes known as acute confusional state, delirium has an acute onset, a fluctuating course, and is associated with serious adverse outcomes such as death, dementia, and the need for long term care.1 Although common in general hospitals (affecting as many as about 30% of inpatients)1 and care homes, delirium is often poorly recognised1; however, it can be prevented in about one third of patients at risk.1 This article summarises the most recent recommendations from the National Institute for Health and Clinical Excellence (NICE) guideline on how to recognise, prevent, and treat delirium.2 NICE recommendations are based on systematic reviews of best available evidence and explicit consideration of cost effectiveness. When minimal evidence is available, recommendations are based on the experience of the Guideline Development Group and their opinion of what constitutes good practice. Evidence levels for the recommendations are given in italic in square brackets. ### Assessment of risk factors [ Based on moderate and low quality evidence from prospective cohort studies ] ### Interventions to prevent delirium