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Health condition · Clinically reviewed

Delirium, acute, fluctuating and often reversible when caught early.

New confusion in an older adult is delirium until proven otherwise. Screen with the 4AT, hunt the trigger, and lean on non-drug care first.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE CG103, Royal College of Physicians and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK guidance including the 4AT, HELP bundle and cautious short-course antipsychotic use.

Key facts

Delirium at a glance.

The essentials in plain English - what it is, why it matters, and how UK teams recognise and treat it today.

  • What it is

    An acute, fluctuating disturbance of attention, awareness and cognition, not better explained by a pre-existing dementia.

  • How common

    20 to 30 per cent of hospital inpatients, up to 50 per cent of older adults, 50 to 80 per cent of ICU patients and about 25 per cent after surgery.

  • Three subtypes

    Hyperactive (agitated), hypoactive (quiet, withdrawn and most often missed) and mixed. Hypoactive carries the worst prognosis.

  • Diagnostic tools

    CAM and the 4AT identify delirium quickly. DSM-5-TR and ICD-11 confirm the diagnosis in specialist settings.

  • It matters

    Delirium raises mortality, length of stay, institutionalisation, long-term cognitive decline and later dementia risk.

  • Treatable

    Most cases resolve when the underlying cause is corrected and non-drug supportive care is delivered well.

Why this guide matters

Common, dangerous, and routinely missed.

Delirium is one of the most frequent things that happens to older inpatients, and one of the most often overlooked. Three ideas underpin the rest of this page.

  • Screen everyone at risk

    The 4AT takes minutes. Every older adult admitted or acutely unwell should be screened, and re-screened when things change.

  • Find and fix the trigger

    Delirium is a symptom, not a diagnosis. PINCH ME points to the cause - infection, medication, dehydration, constipation or pain.

  • Non-drug care comes first

    Reorientation, sensory aids, sleep, family and mobilisation do more than any medication. Antipsychotics are a last resort, not a starting point.

How the diagnosis is made

From new confusion to a clear plan.

The steps a UK ward or acute team will typically follow, in order - so you know what to expect and why.

  1. 01

    Recognising

    4AT at the bedside

    Recommended by NICE. Scores alertness, AMT4, attention and acute change in minutes and flags likely delirium.

  2. 02

    Recognising

    Confirm with CAM

    Acute onset and fluctuating course, plus inattention, plus disorganised thinking or altered consciousness.

  3. 03

    Recognising

    Collateral history

    Family or carers describe baseline cognition, timeline, sleep, alcohol and every recent medication change.

  4. 04

    Confirming

    PINCH ME screen

    Pain, Infection, Nutrition, Constipation, Hydration, Medication, Environment. A structured hunt for the trigger.

  5. 05

    Confirming

    Bloods, urine, ECG, CXR

    FBC, U and Es, LFT, CRP, glucose, calcium, magnesium, phosphate, TFT, B12, folate, cultures, ABG, troponin and urine dip.

  6. 06

    Confirming

    Selective imaging and LP

    CT or MRI head for focal signs, trauma or no clear cause. Lumbar puncture if meningitis or encephalitis is suspected.

  7. 07

    Acting

    Medication review

    Anticholinergics, opioids, benzodiazepines, steroids and polypharmacy are common culprits. Stop or reduce where safe.

Typical timeline: screening the same day, cause identified within 24 to 48 hours.

Symptoms

What delirium actually looks like.

Acute onset, fluctuating attention and altered awareness - in either the loud, hyperactive or the quiet, hypoactive form.

  • Acute onset, fluctuating

    Hours to days, with waxing and waning through the day. Nights are typically worse.

  • Inattention (core feature)

    Unable to follow conversation, count backwards or sustain focus. The single most useful bedside sign.

  • Disorganised thinking

    Rambling, illogical or incoherent speech and difficulty following instructions.

  • Altered consciousness

    Drowsy, hyper-alert or fluctuating between the two. A key clue in the quiet, hypoactive form.

  • Hallucinations and delusions

    Visual hallucinations are more common than auditory. Fleeting persecutory delusions are typical.

  • Sleep-wake reversal

    Awake at night, drowsy by day. Emotional lability, fear and tearfulness are common.

  • Hypoactive presentation

    Withdrawn, quiet and slowed. Often mistaken for depression, tiredness or simply being unwell.

  • Red flag - new confusion

    Any new confusion in an older adult or inpatient is delirium until proven otherwise. Screen the same day.

Treatment

How delirium is treated in the UK.

Treat the cause. Support the brain with orientation, sleep, family and mobility. Use medication only when it is truly needed, in the lowest dose, for the shortest time.

  • Treat the underlying cause

    Antibiotics for infection, oxygen and fluids for hypoxia and dehydration, correct electrolytes, treat pain and relieve constipation or retention.

  • Medication review

    Stop or reduce anticholinergics, opioids, benzodiazepines and unnecessary sedatives. Screen for withdrawal from alcohol or benzodiazepines.

  • Reorientation and environment

    Clocks, calendars, windows, glasses, hearing aids, familiar objects, family at the bedside and a consistent nursing team.

  • Mobilise and hydrate

    Early mobilisation, oral hydration and nutrition, careful bladder and bowel care, minimum restraint and few room moves.

  • Sleep and sensory care

    Protect the sleep-wake cycle with low night-time light and noise. Correct hearing and vision at every interaction.

  • Short-course antipsychotic

    Low-dose haloperidol 0.5 to 1 mg orally or subcutaneously only for severe distress or risk. Review daily. Avoid in Parkinson’s or Lewy body dementia.

  • Alcohol withdrawal delirium

    CIWA-Ar scoring with chlordiazepoxide, diazepam or lorazepam, plus parenteral thiamine (Pabrinex) to prevent Wernicke encephalopathy.

  • Family, MDT and follow-up

    Involve family with a This is Me document, plan discharge with geriatrics, physiotherapy and occupational therapy, and review cognition at 3 to 6 months.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP, geriatrician or acute team knows the person and the context, and can tell you which parts apply. If someone is acutely confused, seek medical review the same day.

  • NICE. Delirium: prevention, diagnosis and management in hospital and long-term care (CG103).

  • Royal College of Physicians. 4AT rapid assessment test for delirium.

  • DSM-5-TR and ICD-11 diagnostic criteria for delirium.

  • European Delirium Association and American Delirium Society joint statement on hypoactive delirium.

Red flags

When confusion needs urgent attention.

Some presentations demand more than a bedside screen. These are the ones that need urgent investigation or a specialist opinion.

  • New confusion in an older adult

    Assume delirium until proven otherwise. Screen with the 4AT the same day and hunt for the trigger.

  • Focal neurological signs

    New weakness, speech change, seizure or unilateral signs need urgent CT head and stroke or neurology review.

  • Suspected meningitis or encephalitis

    Fever, neck stiffness, photophobia or rash means urgent blood cultures, imaging and lumbar puncture.

  • Delirium tremens

    Alcohol withdrawal with autonomic storm, tremor and hallucinations is a medical emergency needing benzodiazepines and thiamine.

  • Wernicke encephalopathy

    Confusion, ophthalmoplegia and ataxia in a malnourished or drinking patient. Give parenteral thiamine before glucose.

  • Non-convulsive status epilepticus

    Fluctuating confusion with subtle motor signs. Consider EEG when delirium does not fit or does not settle.

  • Hypoactive delirium missed as depression

    Quiet, withdrawn patients are still delirious. Missed cases carry the worst outcomes.

  • Rapid deterioration or sepsis

    New confusion with fever, hypotension or tachypnoea is sepsis until proven otherwise. Start the sepsis pathway.

  • Suspected poisoning or overdose

    Consider drug, alcohol or carbon monoxide toxicity and take an urgent toxicology and ABG.

Living with it

After the episode, a longer road home.

Delirium often clears in days, but recovery of thinking, sleep and confidence can take weeks or months. Four ideas make the biggest difference.

A quiet reminder

Recovery is a process, not a switch.

Some people are fully back to baseline in a week. Many are not. Follow-up matters as much as the acute care did.

  1. 01 Recovery

    It can take weeks or months

    Full cognitive recovery after a delirium episode is often slow. Sleep, mood and stamina all take time to return.

  2. 02 Follow-up

    A cognitive review at 3 to 6 months

    Delirium can unmask an underlying dementia. A memory clinic review helps clarify what is temporary and what needs support.

  3. 03 Family

    Ask for a This is Me document

    Sharing baseline habits, routines and preferences with the ward team lowers fear and helps staff spot changes early.

  4. 04 Prevention

    Reduce the next episode’s risk

    Review medications, correct hearing and vision, treat constipation and stay active. Every one of these lowers recurrence.

Frequently asked

Everything we get asked about delirium.

Quick answers on screening, causes, dementia overlap and long-term risk.

  • What is delirium?

    Delirium is an acute, fluctuating disturbance of attention, awareness and cognition that develops over hours to days and is caused by an underlying medical problem, medication or withdrawal. It is not the same as dementia, although the two often overlap.

  • How is delirium different from dementia?

    Dementia is a slow, progressive decline over months to years. Delirium starts suddenly, fluctuates through the day, disturbs attention and consciousness and usually improves once the cause is treated. A person with dementia is at higher risk of developing delirium on top.

  • Why is hypoactive delirium so often missed?

    Quiet, withdrawn, drowsy patients rarely disturb the ward, so they are frequently labelled as tired, low or simply unwell. Hypoactive delirium is more common than the agitated form and has worse outcomes, which is why every unwell older adult should be screened with the 4AT.

  • What are the most common triggers?

    Infection (especially UTI and pneumonia), medications (anticholinergics, opioids, benzodiazepines, steroids), dehydration and electrolyte disturbance, constipation, urinary retention, pain, alcohol or benzodiazepine withdrawal, hypoxia and any acute neurological event.

  • Do we always give antipsychotics for delirium?

    No. Non-drug care - reorientation, sensory aids, family, sleep and mobilisation - is first line. Low-dose haloperidol or an alternative is reserved for severe distress or risk to self or others, given short-term and reviewed daily. Benzodiazepines are avoided unless the cause is alcohol or benzodiazepine withdrawal or seizure.

  • Does delirium cause long-term harm?

    It can. Delirium is linked to higher mortality, longer hospital stays, greater risk of moving to a care home, ongoing cognitive decline and a higher risk of later dementia. Good prevention and prompt treatment reduce, but do not eliminate, that risk.

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