Delirium (acute confusional state) is when someone’s mental function has a sudden change. It comes on quickly, often over hours or days.

As well as showing confusion, people with delirium can be sleepy, agitated, have altered beliefs or see hallucinations.

Delirium is often triggered by:

  • illness
  • the side affects of medication
  • an injury
  • having surgery

Symptoms of delirium

People with delirium may experience symptoms that include:

  • being confused (or more confused than normal)
  • being sleepy and less responsive
  • being very agitated or restless
  • a change in sleeping pattern (like being awake at night and sleeping during the day)
  • suspiciousness or a loss of trust
  • seeing or hearing things that aren’t real

Sometimes these symptoms are worse in the evenings or overnight.

How long does delirium last?

Most delirium lasts a few days but in some cases it can persist for weeks or even months.

Delirium can continue even when all triggers have been addressed. In this situation, you should get ongoing supportive care and help. In other cases, the delirium will slowly improve.

Unfortunately, not all patients recover to the same mental function they had before their delirium.

Causes of delirium

Delirium is caused by a change in the way the brain functions. There are many things that can trigger this, including:

Increased risk of delirium

Anyone can get delirium but some things can increase the risk, including:

  • being over 65
  • having dementia
  • being frail
  • hearing or sight loss
  • having had delirium before
  • alcohol misuse

Delirium is one of the most common medical emergencies. It’s found in around 1 in 7 adults in hospital and about half of patients in intensive care.

Diagnosing delirium

Relatives and carers are often the first to notice signs of delirium. The key change is in the person’s normal mental function.

Healthcare staff identify delirium by assessing the core symptoms. They will often do this using the 4A’s test or 4AT.

4AT is a quick test where a healthcare professional will ask their patient some orientation questions. For example, they could ask what year it is. They could also ask them to give the months of the year in reverse order.

The test helps to show if the patient has a different mental function to normal.

Treatment of delirium

There are different aspects to the treatment of delirium.

Treating triggers

Delirium is usually caused by one or more triggers. Treatment starts by working out what the triggers are. Healthcare professionals can then treat these as effectively as possible. For example, if the person has a chest infection then treating it would help the delirium.

Often more than one trigger may cause delirium. For example a person with a chest infection may also be dehydrated or have a low blood oxygen level. These would also trigger or make the delirium worse.

Treating symptoms

Another important part of delirium care is treating the symptoms of delirium.

Many people become distressed due to feeling disorientated. They may also have paranoia, hallucinations or feel like they’re losing control.

These symptoms can improve with repeated reassurance and by explaining carefully what’s happening. Occasionally, healthcare professionals may use anti-psychotic drugs or other treatments.


Once the triggers and symptoms have been managed, the next step is to help the patient recover.

The aim is to get the person back to their usual self through:

  • rehabilitation
  • engagement with them
  • hydration
  • nutrition

Complications of delirium

Some complications of delirium can include:

  • immobility
  • falls
  • pressure sores
  • isolation

How to support someone with delirium

When caring for someone with delirium, it’s helpful to:

  • ensure hearing aids, glasses and dentures are within reach
  • have a gentle and friendly approach – smile and provide reassurance
  • talk and keep the person informed in short, simple sentences
  • try to make sure someone the person knows well is with them
  • keep a calendar or clock (or both) within view
  • bring in some familiar objects from the person’s home to keep next to their bedside, for example photographs
  • if it’s safe to do so, help the person to eat and drink (check with care staff if you have any doubts)

Caring for someone else can be stressful. Try to ensure you are sleeping and eating and try to create a support network.

What is the long term impact of having delirium?

After recovering from delirium, there’s an increased risk of dementia. People living with dementia who develop delirium may be worse after delirium.

People who have experienced distress during delirium may develop post traumatic stress symptoms. This includes intrusive memories of delirium and symptoms of anxiety and depression.

Delirium when someone’s dying

Delirium is very common in people in their last days of life, affecting up to half of people in this situation.

It’s important to identify the delirium and, where possible, consider if there are easily treatable triggers. However, the main focus of care is in managing the symptoms.

Read more about palliative care

What is the difference between delirium and dementia?

Delirium comes on over hours or days and, in most cases, it will get better in a few days. Dementia develops over months or years and is nearly always irreversible.

Delirium and dementia symptoms can sometimes overlap, for example disorientation is usual in both conditions. However people with delirium are more likely to:

  • be drowsy
  • be agitated
  • be paranoid
  • have hallucinations

The 2 conditions often co-exist, especially in older people. People with dementia are much more likely to develop delirium. In hospital at least half of older people with delirium will also have dementia.

Last updated:
24 May 2024

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