It is well recognised that many older people have dementia but have never been investigated or received a formal diagnosis. If they are admitted to acute hospitals from their own homes or long-term care settings with confusion and little background information about their usual condition, it can be challenging for staff to determine if they have dementia, delirium, delirium superimposed on pre-existing dementia or confusion with a reversible cause such as vitamin deficiency. A careful history and information seeking from carers or family members about their loved one’s pre-admission baseline can inform nursing and medical assessments and help nurses to provide high quality care.