Delirium and Sudden Confusion
A sudden change in awareness, thinking or behaviour can be a medical emergency. Learn how to recognise delirium, why it happens and when to get help fast.
Sudden confusion needs immediate medical help
If someone suddenly becomes confused, cannot answer basic questions, is not making sense or is behaving very differently from normal, call 999 or go to A&E.
Do not assume it is dementia or try to diagnose the cause yourself. Sudden confusion can sometimes be life-threatening.
Do not drive the person to A&E yourself if it is unsafe. Ask someone else to drive or call 999 for an ambulance.
- 20–30%
of people on medical wards in hospital have delirium at any one time.
Source: NICE clinical guideline CG103
- 10–50%
of people having surgery develop delirium.
Source: NICE clinical guideline CG103
What is delirium?
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.
Possible signs of delirium
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- Becoming unusually quiet, withdrawn or sleepy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.
Can a UTI cause delirium?
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
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.
Delirium can have many causes
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.
What to do while waiting for help
- 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
Delirium and dementia are different
- Usually begins suddenly
- Symptoms may change during the day
- Often has an underlying medical cause
- Requires urgent medical assessment
- Usually develops gradually
- Causes longer-term changes in memory and thinking
- A person with dementia can still develop delirium
Never assume a sudden change is simply part of dementia.
See our page on dementia for background on the condition and long-term support.
Call 999 if the person appears seriously unwell
Warning signs can include confusion or slurred speech, severe difficulty breathing, blue, grey, pale or blotchy skin, uncontrollable shivering, or passing very little or no urine.
Related pages on Sixpence Support UK
- 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.
Where this information comes from
Official sources used on this page
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.
- [1] NHS. Sudden confusion (delirium) · 2024
- [2] NHS. Urinary tract infections (UTIs) · 2024
- [3] NHS. Sepsis · 2024
- [4] Guy's and St Thomas' NHS Foundation Trust. Delirium (sudden confusion) · 2024