If an older relative has suddenly become confused, over hours or a few days, treat it as urgent. The NHS says to go to A&E or call 999 if someone suddenly becomes confused. Many causes need to be assessed and treated quickly, and some can be life threatening.
Sudden confusion is often delirium. NICE describes delirium as a common condition that comes on quickly and tends to come and go. It usually develops over 1 to 2 days. It is caused by something else going on in the body, such as an infection, a medicine, dehydration or a stroke.
Delirium is not the same as dementia, although the two can overlap. NICE says delirium can be prevented and treated if dealt with urgently, and that it is usually temporary.
Get help now
Call 112 or 999 in Ireland, 999 in the UK or 911 in the US, or go to an emergency department, if someone:
Do not drive them yourself. Call for an ambulance or ask someone else to drive. Bring their medicines with you.
Contact a GP if an older person you care for may have a urine infection.
See a GP (non-urgent) if someone has become more forgetful or confused gradually, over months.
The NHS says a person who is confused may:
It suggests asking the person their name, their age and today's date. If they seem unsure or cannot answer, they probably need medical help.
NICE lists the kinds of change, over hours or days, that may point to delirium:
NICE says these changes may be reported by a carer or relative. You often notice them first, because you know what is normal for your relative.
NICE describes two main types of delirium:
Some people have both. NICE says hypoactive delirium is often missed. Watch for withdrawal, slow responses, moving less, poor concentration and eating less. A relative who is "just very sleepy and not themselves" may need help as urgently as one who is agitated.
NICE says a person is at risk of delirium if they:
Delirium can start before someone reaches hospital, or develop during a hospital or care home stay. NICE says about 20% to 30% of people on hospital medical wards have delirium. It says 10% to 50% of people having surgery develop delirium. In long-term care, the figure is under 20%.
The NHS lists some of the most common causes of sudden confusion:
The HSE lists "changes in behaviour in older people, such as severe confusion or agitation" as a UTI symptom. It also lists confusion and disorientation as signs of serious dehydration needing emergency care.
Delirium often has more than one cause at once. NICE asks clinicians to look at a range of factors. These include infection, dehydration, constipation, low oxygen, pain, poor nutrition, poor sleep and problems with sight or hearing. It also recommends a medication review for people taking several medicines.
Some medicines can cause or add to confusion. Our article on anticholinergic burden explains one group that is often involved in older people.
Never stop or change a prescribed medicine on your own. Some are dangerous to stop suddenly. Bring a list, or the medicines themselves, to the doctor.
Delirium can be the first sign of something serious:
It can be hard to tell the difference. NICE says some people have both. The pattern over time is the biggest clue.
There are exceptions. The NHS says vascular dementia can sometimes develop suddenly and quickly get worse. In dementia with Lewy bodies, the HSE says confusion or sleepiness can change over minutes or hours. Read more about why Lewy body dementia gets missed.
People with dementia are at higher risk of delirium. A sudden change in someone who already has dementia is not "just the dementia getting worse" until a doctor has checked.
If there is doubt between delirium and dementia, NICE says clinicians should treat the delirium first.
NICE says a trained health or social care practitioner should use a short assessment called the 4AT if they notice signs of delirium. A doctor or other qualified professional then makes the diagnosis.
The main treatment is finding and treating the cause, or causes. The HSE says a urine sample may be tested if a UTI is suspected. Other tests depend on what the doctor finds.
NICE also recommends:
NICE notes the risks of haloperidol in older people. It highlights people with Parkinson's disease or dementia with Lewy bodies. If your relative has either condition, make sure the team knows.
If delirium does not clear, NICE says clinicians should look again for causes. They should also follow up for possible dementia.
Your knowledge of the person matters. NICE asks staff to encourage families to report sudden changes in behaviour.
While waiting for help, the NHS suggests:
NICE lists ways care teams help prevent and manage delirium. Families can support many of them:
NICE says delirium is common and usually temporary. It also says delirium is linked to longer hospital stays, falls, a higher chance of dementia and a higher risk of death. That is why quick treatment matters.
NICE encourages people to talk about their experience of delirium during recovery. Some people find it frightening to remember.
If your relative's thinking does not return to normal, ask their GP about a memory assessment. Our guide to cognitive screening tests explains what happens. For slower changes, see memory worries: normal ageing or not.
In Ireland, if it is outside surgery hours, our guide to out-of-hours GP and urgent care explains your options. For sudden confusion, call 112 or 999.
Yes. The NHS says UTIs are a common cause of sudden confusion in older people or people with dementia. The HSE lists severe confusion or agitation as a UTI symptom in older people. Contact a GP, or call 112 or 999 if confusion is sudden or severe.
NICE says it is usually temporary, but does not give a set time. It depends on the cause and how quickly it is treated. If it does not clear, doctors should look again for causes.
Not necessarily. Delirium has a cause that can often be treated. But NICE links delirium with a higher chance of later dementia, so follow-up matters if thinking does not recover.
Yes. NICE describes "hypoactive" delirium, where people become withdrawn, quiet and sleepy. It says this type is often missed. Get medical help for any sudden change.
This article is general information, not medical advice. It cannot diagnose the cause of anyone's symptoms. If someone has suddenly become confused, get medical help straight away.
Reviewed by: Proco Team
Last updated: November 2026