Delirium and Sudden Confusion

Delirium is a sudden change in a person's awareness, thinking or behaviour. It may develop over a few hours or days.

It is different from dementia, which usually develops gradually. However, a person with dementia can also develop delirium.

Delirium is more common in older people, people with dementia, people who are seriously unwell and people who are in hospital or a care setting.

Signs can include:

• Suddenly appearing confused or disorientated
• Not knowing where they are or what day it is
• Being unable to answer simple questions
• Speaking in a way that does not make sense
• Becoming unusually agitated, frightened or restless
• Becoming unusually quiet, withdrawn or sleepy
• Having difficulty concentrating
• Seeing or hearing things that are not there
• Acting very differently from normal
• Symptoms changing throughout the day

Not everyone will have every symptom.

A urinary tract infection, commonly called a UTI, can sometimes cause changes in behaviour, agitation or confusion in older or frail people, people with dementia and people who use a urinary catheter.

Other possible UTI signs may include:

• Pain or burning when passing urine
• Needing to urinate more often or urgently
• Cloudy urine or blood in the urine
• Lower abdominal or back pain
• A high or low temperature
• New shivering or shaking
• New or worsening incontinence
• Feeling weak or generally unwell

A UTI is only one possible cause of sudden confusion. Sudden confusion should not automatically be treated as a UTI without a proper medical assessment.

NHS information about UTIs →

Sudden confusion or delirium can be caused by:

• Other infections
• A stroke or transient ischaemic attack (TIA)
• Low blood sugar
• Dehydration
• Medication side effects or medication changes
• Head injury
• Heart or lung problems
• Seizures
• Alcohol poisoning or withdrawal
• Carbon monoxide poisoning
• Severe illness, including sepsis

Please do not try to decide which condition is responsible yourself. A doctor needs to examine the person and run the right tests.

• Stay with the person and keep them safe
• Speak calmly using short, simple sentences
• Remind them who you are and where they are
• Avoid asking lots of questions
• Do not physically restrain them unless they are in immediate danger
• Gather their medicines or a current medication list
• Tell medical staff when the confusion started and what changed
• Mention any recent illness, falls, medication changes or problems eating, drinking or passing urine

Never assume a sudden change is simply part of dementia.

See our page on dementia for background on the condition and long-term support.

• Dementia — background, care and long-term support.
• Care after hospital — what to expect when someone leaves hospital.
• Ambulances and medical transport — 999, 111 and non-emergency transport.
• Find local services — NHS finders for GP, A&E, pharmacy and more.
• Support directory — carers' support and older people's services.

Official sources used on this page:

• NHS — Sudden confusion (delirium)
• NHS — Urinary tract infections
• NHS — Sepsis
• Guy's and St Thomas' NHS Foundation Trust — Delirium

This page provides general information and is not a diagnosis or a replacement for professional medical care. Always seek the advice of a qualified health provider about a specific person's condition. In an emergency, call 999.