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Alternate Names

  • confusional state
  • mental dysfunction


Confusion is an abnormal mental condition or state of mind. A person who is confused has trouble understanding the environment and may react or respond inappropriately to it.

What is going on in the body?

Confusion is often a sign of an underlying problem or illness. The causes range from mild to serious. Confusion may come on suddenly or may occur gradually over time. Many causes of confusion are reversible.


What are the causes and risks of the symptom?

There are many possible causes of confusion, including:
  • being in an unfamiliar situation. For example, roughly 30% of people who get admitted to a hospital intensive care unit become confused during their stay. Being sick and in an unusual situation causes enough stress to make many people become confused.
  • a sudden illness, especially when the illness is severe. This is most likely to occur in young children and elderly persons. Even the flu can cause confusion in some people. Other infections, such as the brain infections meningitis and encephalitis, and a serious blood infection called sepsis, commonly cause confusion.
  • medications, especially when several are given in high doses at once, for acute illness
  • illegal drugs or alcohol
  • withdrawal from drugs or alcohol
  • low blood sugar, known as hypoglycemia
  • head injury
  • brain damage, such as that from Alzheimer disease, multiple sclerosis, Parkinson disease, a brain tumor, or a stroke
  • fluid and salt imbalances, such as low sodium
  • vitamin or mineral deficiency, such as thiamine or vitamin B12 deficiency
  • chronic or serious infections or illnesses, such as HIV, syphilis, appendicitis, chronic obstructive pulmonary disease, cirrhosis, chronic renal failure, anemia, cancer or heart attacks
  • hormone imbalances, such as low thyroid levels or hypothyroidism
There are many other causes of confusion. Sometimes, a cause cannot be found.


What can be done to prevent the symptom?

Prevention is related to the cause of the confusion. For example, avoiding certain drugs can prevent the confusion that can be caused by them. Wearing a helmet when riding a bike or motorcycle and following sports safety guidelines for children, adolescents, and adults can help prevent head injuries. However, many causes cannot be prevented.


How is the symptom diagnosed?

When someone is confused, the healthcare professional will try to determine the cause. Sometimes it is obvious from a medical history and physical exam. However, further testing is often needed. Blood tests are commonly done to help check for salt or hormone imbalances, liver disease, and many other conditions.
Urine testing can help rule out an infection or kidney problem. A chest X-ray can be done to look for lung conditions, such as pneumonia. Other tests may be needed in some cases. For example, if the clinician suspects a stroke or brain tumor, it can be seen on a cranial CT scan.

Long Term Effects

What are the long-term effects of the symptom?

Long-term effects are related to the cause of the confusion. For example, confusion caused by an infection often goes away once the person gets over the infection. An individual with cancer or chronic liver disease often dies from those conditions. In some people, confusion may get worse over time and become permanent, such as in Alzheimer disease, alcoholism, or AIDS.

Other Risks

What are the risks to others?

Confusion itself is not contagious and poses no risk to others. If confusion is the result of an infection, the infection may be contagious.


What are the treatments for the symptom?

Treatment is directed at the cause of the confusion.
  • A person who develops confusion while in the hospital may simply need someone to reorient him or her to the time and place.
  • An individual with low blood sugar may need to drink a sweet drink or eat a snack.
  • A person who formerly used drugs usually gets better when the drug is stopped.
  • An individual with an infection may need antibiotics.
  • A person with kidney failure may need dialysis, which is a procedure that filters the blood when the kidneys don't work.
  • Someone with cancer may need chemotherapy, radiation therapy, or surgery.

Side Effects

What are the side effects of the treatments?

All medicines have possible side effects. For example, antibiotics may cause allergic reactions or stomach upset. Surgery can be complicated by bleeding, infection, or an allergic reaction to the anesthetic.

After Treatment

What happens after treatment for the symptom?

In many cases, confusion goes away when the cause is treated. In other cases, confusion may be a sign of more serious disease. Some causes of confusion such as stroke and Alzheimer disease may cause permanent brain damage and problems with brain function.


How is the symptom monitored?

A confused person should not be left alone. Other monitoring depends on the underlying cause. For example, those who have had a stroke often need close monitoring in an intensive care unit at first. Any new or worsening symptoms should be reported to the healthcare professional.


Harrison's Principles of Internal Medicine, 1998, Fauci et al.

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