Sudden Confusion (Delirium): symptoms, self-care and when to get help
Checked against current published health guidance — last reviewed 2026-09-23. See how we check.
Sudden confusion, known as delirium, is a change in someone's thinking or behaviour that develops over hours or days. It is common in older people and is often caused by an infection, dehydration or medicine. It needs urgent medical attention the same day, and it is an emergency if it comes with signs of a stroke, breathing difficulty or someone cannot be woken.
Overview
Someone with delirium may seem muddled, not know where they are, have trouble following a conversation, be unusually sleepy or agitated, or see things that are not there. Symptoms often come and go and can be worse at night.
Delirium is different from dementia, which develops slowly over months or years, but people with dementia are more likely to get delirium. A sudden worsening in someone with dementia should also be treated as urgent. Common causes include urine and chest infections, dehydration, constipation, low blood sugar, pain and changes to medicines.
What may help
- Stay with the person and keep them calm, speaking clearly and simply
- Make sure they have their glasses and hearing aids
- Offer drinks if they can swallow safely
- Note when the confusion started and any other symptoms, and make a list of their medicines to share with health professionals
When to see a pharmacist or GP
- Any sudden confusion needs medical assessment the same day: contact the GP urgently or an urgent care service
- Confusion that comes and goes over a few days
- A change in behaviour after starting or changing a medicine
When it could be an emergency
- Signs of a stroke: face drooping, arm weakness or slurred speech
- Difficulty breathing, chest pain, or blue, grey or blotchy skin
- The person cannot be woken, is very drowsy or has had a fit (seizure)
- Confusion after a head injury
- Signs of sepsis, such as a high or very low temperature with feeling very unwell
If any of these apply, don't wait — call your local emergency number (see emergency numbers by country, or Red Flags in the app), or go straight to your nearest emergency department.
Want more detail, tailored to your own situation?
Look up "Sudden Confusion (Delirium)" in the appCommon questions
What is the difference between delirium and dementia?
Delirium comes on suddenly, over hours or days, and is often caused by something treatable such as an infection. Dementia develops gradually over months or years.
Can a urine infection cause confusion in older people?
Yes. Urine infections are a common cause of sudden confusion in older people, as are chest infections and dehydration.
Does delirium go away?
It usually improves once the cause is treated, although it can take days or weeks to clear completely.
Is sudden confusion an emergency?
It always needs urgent medical attention the same day. Call your local emergency number if it comes with stroke signs, breathing difficulty, or the person cannot be woken.
Official sources
Related topics
Early Signs of Dementia
Memory changes to look out for and getting a diagnosis.
Urinary Tract Infection (UTI)
Symptoms, self-care, and when it's serious.
Dehydration in Older People
Signs to watch for and simple ways to help.
Stroke Signs (FAST)
Recognise a stroke with FAST and act immediately.
Sepsis Signs
A life-threatening reaction to infection: know the signs.
General information only, last checked 2026-09-23 — not medical advice and not a diagnosis. This page doesn't cover every cause or every person's situation; for anything specific to you or someone in your care, speak to a pharmacist, GP, or other qualified professional. See how we check. Be Health Wise is part of the Be Wise family of apps.