Delirium - symptoms, diagnosis and treatment

Delirium is a common, serious but often treatable condition that starts suddenly in someone who is unwell. It’s much more common in older people, especially those with dementia.

What is delirium?

Delirium is a worsening or change in a person’s mental state that happens suddenly, over one to two days. The person may become confused, or be more confused than usual. Or they may become sleepy and drowsy. Delirium can be distressing to the person and those around them, especially when they don’t know what’s causing these changes.

Delirium may be the first sign that someone is becoming unwell, and is one of the most common early symptoms of coronavirus infection in people with dementia.

What are the symptoms of delirium?

If someone suddenly develops any of the symptoms below or is ‘not themselves’, speak to a nurse or doctor immediately. Family, friends and carers – including professional carers – are often best placed to recognise and describe changes because they know the person best. A person with delirium may be unaware of the changes and will often be unable to describe them.

A person with delirium may:

  • be easily distracted
  • be less aware of where they are or what time it is (disorientation)
  • suddenly not be able to do something as well as normal (for example, walking or eating)
  • be unable to speak clearly or follow a conversation 
  • have sudden swings in mood
  • have hallucinations – seeing or hearing things, often frightening, that aren’t really there
  • have delusions or become paranoid – strongly believing things that are not true, for example that others are trying to physically harm them or have poisoned their food or drinks.

Symptoms of delirium often fluctuate (come and go) over the course of the day. Healthcare professionals divide delirium into three types based on the other symptoms that someone has. These three types are hyperactive, hypoactive and mixed delirium. Among older people, including those with dementia, hypoactive and mixed delirium are more common.

Hyperactive delirium

A person with hyperactive delirium may:

  • seem restless
  • be agitated (for example, with more walking about or pacing)
  • resist personal care or respond aggressively to it 
  • seem unusually vigilant.

Someone with hyperactive delirium can easily get very distressed due to not understanding where they are or losing track of time. They may have delusions or hallucinations that carers are trying to harm them.

Hypoactive delirium

A person with hypoactive delirium may be:

  • withdrawn, feeling lethargic and tired
  • drowsy 
  • unusually sleepy
  • unable to stay focused when they’re awake.

It can be easy not to notice that someone has hypoactive delirium, because they may be very quiet. The person may stop eating as much or become less mobile than usual. They may spend more time in bed. 

Mixed delirium

A person with mixed delirium has symptoms of hyperactive delirium at times and symptoms of hypoactive delirium at other times. They will switch between these symptoms over the day or from one day to the next. For example, they could be very agitated at one time and then later become very drowsy.

How is delirium different from dementia?

Delirium is different from dementia. But they have similar symptoms, such as confusion, agitation and delusions. If a person has these symptoms, it can be hard for healthcare professionals who don’t know them to tell whether delirium or dementia is the cause. When a person with dementia also gets delirium they will have symptoms from both conditions at once.

There are important differences between delirium and dementia. Delirium starts suddenly (over a period of one to two days) and symptoms often also vary a lot over the day. In contrast, the symptoms of dementia come on slowly, over months or even years. So if changes or symptoms start suddenly, this suggests that the person has delirium.

Dementia with Lewy bodies is an exception. This type of dementia has many of the same symptoms as delirium (including visual hallucinations) and they can vary a lot over the day.

Other symptoms of dementia

Dementia can cause a number of different symptoms. Here we explain some of these changes and suggest practical ways to manage them.


How is delirium diagnosed?

It’s really important that a person’s delirium is diagnosed quickly. Delirium is a serious condition and is linked to severe problems if it isn’t treated.

A healthcare professional such as a doctor or nurse will make the diagnosis. To decide if someone has delirium or not, they will consider the person’s clinical history (how their symptoms developed) and examine them. They will use a quick test known as a 4AT.

The 4AT test measures someone’s:

  • alertness – whether the person is drowsy or agitated
  • awareness – for example, of the current year and where they are
  • attention – for example, how well the person is able to name the months of the year backwards from December
  • acute change or fluctuating course – whether symptoms started suddenly or are now coming and going. 

A doctor or nurse may assess someone’s mental state each day in hospital. Or they may do so when the person moves from one place to another, for example from a hospital to a care home. If they find that the person has delirium, they should tell the person’s close family. 

Health or social care staff involved in their care might suspect that the person has undiagnosed dementia, but will not assess them for this until their delirium is over. If they are in doubt, they will treat the delirium first as this needs treating more urgently.

Even in hospital it can be difficult for delirium to be spotted and diagnosed. This is another reason to tell staff if you notice a change in the person you care about. 

As well as diagnosing the person’s delirium, healthcare professionals will do other tests to work out what has caused the delirium. For example, they may take blood samples or possibly a chest x-ray. This is important because treating the cause of the delirium will usually help the person’s symptoms improve or go away.

Who gets delirium and why? 

Delirium is common, particularly among older people in hospital. It’s usually the reaction of the brain to a separate medical problem (or several medical problems at once). Problems that can cause delirium include:

  • pain
  • infection
  • poor nutrition
  • constipation (not pooing) or urinary retention (not peeing)
  • dehydration
  • low levels of blood oxygen
  • a change in medication
  • abnormal metabolism (for example, low salt or blood sugar levels)
  • an unfamiliar or disorientating environment. 

Anyone can get delirium, but the following factors put people at higher risk:

  • dementia – this is the biggest single risk factor for delirium
  • aged over 65
  • frailty 
  • multiple medical conditions
  • poor hearing or vision
  • taking multiple medications (for example, antipsychotics, benzodiazepines and certain antidepressants)
  • having already had delirium in the past.

Delirium is common in older people in hospital, because they are unwell or may have had an operation (for example, hip or heart surgery). Hospital staff should speak to the patient and family beforehand about the risk of delirium after the operation. Intensive care is another very common cause of delirium in hospital. 

Delirium is also quite common in residents of care homes, or in older people with dementia at home. They are more likely to be frail, have several health conditions and be taking several medicines.

When someone goes into hospital or a care home, it’s helpful if they have a completed or updated copy of a form such as This is me with them. Care staff can refer to this for information about the person, which will be particularly helpful if they get delirium during their stay.

With the right care, some cases of delirium can be prevented. Soon after a person comes into hospital or long-term care, staff should check whether they are at risk of delirium. If they are, there are non-drug approaches to help prevent delirium that should be put in place, including those described below.

What is treatment and support for delirium?

Delirium is treated first by addressing the medical problem(s) that have caused it. For example, if the person has low blood oxygen or low blood sugar levels these will be corrected quickly. If the person has an infection they may be given antibiotics. If they are in pain, constipated or not passing urine then these will be treated. 

Doctors will also review the person’s medication and stop any non-essential drugs that may be linked to delirium. Staff will make sure the person is supported to eat and drink regularly.

Delirium will usually improve if its cause is found and treated.

A supportive and calm environment can also help someone recover from delirium. Nursing staff, and visiting family and friends, can all help by: 

  • talking calmly to the person in short clear sentences, reassuring them as to where they are and who you are 
  • supporting the person with familiar objects from home, such as photographs 
  • making sure that any hearing aids and glasses are clean and working and that the person is wearing them
  • setting up a 24-hour clock and calendar that the person can see clearly
  • helping the person develop a good sleep routine, including reducing noise and dimming lights at night
  • reassuring the person if they have delusions
  • supporting the person to be active – to sit up or to get out of bed – as soon as they safely can
  • helping the person to eat and drink regularly
  • not moving the person unnecessarily – either within and between hospital wards, or into hospital if delirium is being managed at home.

Doctors won’t normally give someone medication to treat delirium, because there is very little evidence that drugs help. Drugs should be considered only if the person’s behaviour (for example, severe agitation in hyperactive delirium) poses a risk of harm to themselves or others, or if hallucinations or delusions are causing the person severe distress. 

In either case a doctor may try a low dose of a sedative or an antipsychotic for a few days. (Doctors won’t give an antipsychotic to a patient with Lewy body dementia, because of the risk of side effects.)

After delirium

The symptoms of delirium get better in most people over a few days to weeks, once the underlying cause is treated. However, delirium usually means a person will have to stay longer in hospital. When they do leave, their medical notes and their care and support plan should record their delirium and include what further support they will need. 

Although some people recover fully, delirium can also have lasting consequences after it has been treated. These are more common in older people.

  • A person may have distressing memories of delirium, sometimes linked to feelings of fear or anxiety, for months afterwards. Those close to the person should support them to talk openly about their experience and feelings. If they’ve kept a diary of the person’s time with delirium, they can use this to help the person make sense of their experience once they’re getting better.
  • Delirium is linked to a faster worsening of a person’s mental abilities and function. A person with dementia may have been able do something (for example, dress themselves) before delirium but are no longer able to afterwards. This change can be permanent. Some people who have had delirium will now have additional needs which are best met by them going into a care home. 
  • In some cases a person will not have a diagnosis of dementia when they go into hospital, but after having delirium their symptoms will get worse and they will later be diagnosed with dementia. In these cases the delirium seems to have ‘uncovered’ the person’s dementia.

These complications are more likely after delirium but they’re not inevitable. However, they do mean it’s important to be aware of delirium and try to prevent it where possible.