Delirium Diagnosis

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Delirium refers to a disturbed mental state that causes confusion and decreased awareness of a person’s environment. It often has a sudden onset but usually resolves when the underlying cause is treated. Some examples of contributing factors include the following:

  • Older age
  • Memory problems
  • Terminal illness
  • Recent surgery
  • Poor hearing or eyesight
  • An illness that affects the brain, such as head injury or stroke
  • Drug or alcohol abuse
  • The use of certain medications

Also known as an “acute confusional state,” delirium can be a frightening condition for both the sufferer and those around them.

Image Credit: fran_kie / Shutterstock
Image Credit: fran_kie / Shutterstock


A doctor will diagnose delirium based on the signs and symptoms of the condition. These signs and symptoms often develop over a short space of time, within a few hours or days. They may also come and go throughout the day, meaning there may be periods where there is no indication of delirium. Some of the main signs and symptoms of delirium are described below.

Reduced awareness of surroundings

Some signs that a person is experiencing reduced awareness of their environment include:

  • Inability to concentrate on one topic
  • Being concerned with one idea and avoiding conversation or questions
  • Short attention span
  • Getting distracted by insignificant things
  • Withdrawal from activities

Cognitive impairment

Signs that a person’s thinking skills may have been affected include:

  • Reduced memory ability
  • Poor understanding of speech
  • Speaking nonsense or rambling
  • Difficulty speaking
  • Disorientation over a location, who people are, or the time of day
  • Difficulty reading, writing, or recalling words.

Changes in behavior

Someone may have developed behavioral changes if they:

  • Hallucinate
  • Experience sleep disturbances
  • Become agitated, irritable, or restless
  • Experience strong emotions such as anxiety, anger, or fear

Delirium and dementia

Delirium and dementia can present with similar symptoms, and any input from friends, family members or caregivers regarding any changes in a person’s thinking, behavior and abilities can be very helpful to a doctor in making an accurate diagnosis. Some ways in which a doctor can tell the difference between delirium and dementia are described below.

  • Attention span – In cases of delirium, a person is often unable to stay focused, while people are generally alert during the initial stages of dementia.
  • Onset – Delirium has a short onset, occurring within a few hours or days, while dementia is a slowly progressing disease that first presents with only minor symptoms.
  • Fluctuation in symptoms – Delirium symptoms often fluctuate, coming and going throughout the day, while in dementia, memory and thinking skills remain fairly constant.


Some of the tests a doctor will use to identify symptoms of delirium are described below.

  • Mental status assessment - A doctor may try to assess mental awareness, cognitive ability and attention informally through conversation or by using checklists designed to screen a patient’s mental state.
  • Physical examination - A physical examination of the patient can be used to provide clues about any underlying conditions causing the delirium. The exam may reveal an infection, dehydration or alcohol withdrawal, for example.
  • Neurological examination - An examination of coordination, nervous reflexes, vision and balance can help a doctor identify whether a stroke or other neurological problem has occurred.
  • Other tests - A blood, urine or other diagnostic tests may also help provide important clues about what might be causing the delirium.


Once delirium has been diagnosed, it can only be treated once the cause is also diagnosed. If the cause is an infection, for example, antibiotics can be prescribed to resolve the problem. Once the cause has been identified, delirium often gets better quickly, within a couple of days or weeks.

Audrey Curtis's Experience with Delirium

Further Reading

Last Updated: Dec 23, 2022

Sally Robertson

Written by

Sally Robertson

Sally first developed an interest in medical communications when she took on the role of Journal Development Editor for BioMed Central (BMC), after having graduated with a degree in biomedical science from Greenwich University.


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