Delirium is an acute and fluctuating syndrome characterized by impaired consciousness and attention, accompanied by changes in cognition or perception, and commonly occurs in older adults with underlying medical conditions. It can be hyperactive, hypoactive, or mixed, with risk factors including older age, visual impairment, brain disorders, serious illness, dehydration, metabolic abnormalities, depression, polypharmacy, and major surgery, while precipitating factors include acute illness, urinary tract infection, hyponatremia, hypoxemia, shock, anemia, pain, and intensive medical procedures. Delirium should be distinguished from infection in older adults because delirium typically has a sudden onset, impaired attention and consciousness, fluctuating cognition, and may include hallucinations, whereas infection generally has a more gradual course and preserved consciousness and attention unless severe. Management focuses on identifying and treating the underlying cause, providing supportive and non-pharmacological care such as hydration, reorientation, adequate lighting, familiar surroundings, family involvement, and physical mobility, with antipsychotic medication considered when necessary for severe agitation or psychotic symptoms. Most delirium symptoms resolve within about a week when the underlying cause is treated, although some older adults may require several weeks or may not fully return to their previous level of functioning.