Sudden confusion is not always dementia

Quick summary

If someone becomes confused over hours or a day or two rather than over months, that is usually delirium, not dementia. Common causes include infection, dehydration and medication. It is often treatable, and it needs urgent medical help. The NHS advice is to go to A and E or call 999 if someone suddenly becomes confused.

What is delirium?

A sudden change in someone’s mental state. They may be unable to think or speak clearly, not know where they are, struggle to pay attention, or see and hear things that are not there (NHS, Sudden confusion).

Some people become agitated and restless. Others become quiet, drowsy and withdrawn, which is easier to miss because it does not look like confusion. Symptoms often change through the day and are frequently worse in the evening and at night.

Delirium is common in older people, particularly those who already have dementia, and in people who are unwell or in hospital.

Delirium or dementia?

The two can happen together. Someone with dementia can develop delirium on top, and it can look like their dementia has suddenly got much worse. The question to ask is whether they are more confused than they were a few days ago. Families usually notice this before anyone else.

What should I do?

The NHS is direct about this. Go to A and E or call 999 if someone suddenly becomes confused, because many causes need to be assessed and treated as soon as possible, and sometimes they can be life threatening. Do not drive them to A and E yourself if that is not safe. Take their medicines, or a list of them, with you (NHS).

The NHS suggests a simple check: ask the person their name, their age and today’s date. If they seem unsure or cannot answer, they probably need medical help.

If the change has been gradual, over months, that is a GP appointment rather than an emergency.

While you wait

The NHS gives practical advice for this.

• Stay with them. Tell them who you are and where they are, and keep reassuring them.
• Use simple words and short sentences.
• Write down their medicines if you can.
• Do not ask lots of questions while they are confused.
• Do not stop them moving around unless they are in danger.

What causes it?

The NHS lists common causes of sudden confusion, including:

• An infection. Urinary tract infections are a common cause in older people and people with dementia. Chest infections are another.
• A stroke or TIA.
• Low blood sugar in someone with diabetes.
• A head injury, which is one reason confusion after a fall always needs checking.
• Some prescription medicines.
• Alcohol, including withdrawal.
• Carbon monoxide poisoning, especially if others in the house also feel unwell.
• Serious lung or heart problems.

Dehydration, constipation, pain and poor sleep also commonly contribute, and it is often a combination rather than a single cause.

A note on urine tests

Families often expect a urine dipstick test, and sometimes buy them to use at home. UK guidance advises against using dipsticks to diagnose a urine infection in people over 65, because up to half of older adults have bacteria in their urine without having an infection, which gives a positive dipstick result either way.

That means a positive home test does not confirm a urine infection, and a negative one does not rule out the other causes of delirium. A clinician needs to assess the whole picture. 

How long does delirium last?

It varies. Some people improve within hours or days once the cause is treated. For others, particularly frail older people and people with dementia, it can take weeks, and some people are left weaker or less confident than before.

Having delirium once makes it more likely to happen again. It is worth asking the GP what to look out for, and making sure the episode is recorded in their notes.

Reducing the risk

Not every episode can be prevented, but some things help.

• Enough to drink, particularly in hot weather and during illness.
• Glasses and hearing aids worn and working.
• A clock and calendar where they can be seen.
• Good sleep, with a regular routine and light during the day.
• Regular medication reviews, especially when new medicines are added.
• Watching for constipation and pain, which are easily missed in someone who cannot easily say.

Frequently asked questions

Can a urine infection cause confusion?

Yes. The NHS lists urinary tract infections as a common cause of sudden confusion in older people and people with dementia. Sudden confusion still needs urgent assessment, because it may have other causes.

Should I call 999 or the GP?

For sudden confusion, the NHS says go to A and E or call 999. For gradual forgetfulness or confusion over months, see a GP. If you are unsure, NHS 111 can advise.

My mum has dementia and seems much worse this week. Is that delirium?

It could be. A sudden worsening over days is not the usual pattern of dementia, and it should be assessed urgently rather than put down to the dementia progressing.

Will they go back to how they were?

Many people do once the cause is treated, though recovery can be slow, especially for frail older people. Some people take longer to regain their previous level.

Can I prevent it happening again?

Not always, but drinking enough, wearing glasses and hearing aids, good sleep and regular medication reviews all help reduce the risk.

About Visiting Angels Cheshire East

Visiting Angels Cheshire East provides care at home across Macclesfield, Wilmslow, Knutsford, Congleton, Alsager and the surrounding villages, along with Buxton, Whaley Bridge and the Staffordshire Moorlands towns.

• You see the same faces. Our carer turnover is 12 per cent, against a sector figure of 23.7 per cent (Skills for Care, 2025). A carer who knows someone well is more likely to notice when they are not themselves.
• Carers trained in dementia, Parkinson’s, stroke recovery and complex care.
• You choose your caregiver. You meet them before care starts, and if it is not right you say so and we send someone else.
• No visit is ever shorter than an hour, with time to make sure drinks and meals are actually taken.
• Short term support available after a hospital stay, while someone recovers.

Alan’s wife is supported at home, and this is what he wrote:

“Excellent in every respect. Staff are caring, friendly and helpful. [Our carers] do everything they can to make my wife’s life easier. Management and staff are flexible in their approach and do the unpleasant jobs with a smile and willingness which is commendable. They are always willing to ‘go the extra mile.'”

Alan Hallett, Google review

Not sure what you need yet? Start with a free assessment

Our free home care assessment is a visit at a time that suits you, with no obligation afterwards. In it we will:

• Work out what is actually difficult, and which times of day, which is usually what a visit should be built around.
• Talk through a realistic package, what it would cost, and how it should change as they recover.
• Look at the money with you, and point you towards the funding, benefits and grants you may be entitled to.
• Tell you honestly if you do not need us yet, or if someone else is a better fit.

If someone has come home after an episode of delirium and you are working out what support they need, call us on 01625 720157. You can also send an enquiry, and you can see what our services cover.

Authored by Dr Niall Jawad, Director, Visiting Angels Cheshire East.

Published 21 September 2026. Last updated 21 September 2026.

This article is general information, not medical advice, and no substitute for urgent assessment by a clinician. It cannot diagnose delirium, dementia or any other condition. If someone becomes suddenly confused, go to A and E or call 999. The author is a director of the company and is not acting in a clinical capacity, and Visiting Angels Cheshire East provides personal care at home rather than medical or nursing care. To the fullest extent permitted by law, GB Care at Home Ltd accepts no liability for any loss or injury arising from reliance on this article.