Decreased alertness is a state of reduced awareness.

A coma is a state of decreased alertness from which a patient cannot be awakened. A long-term coma is called a vegetative state.

See also:

• Delirium
• Dementia

Stuporous; Mental status - decreased; Loss of alertness; Decreased consciousness; Changes in consciousness; Obtundation; Coma; Unresponsiveness

Many conditions can cause decreased alertness, including:

• Chronic kidney disease
• Extreme tiredness or lack of sleep
• High blood sugar or low blood sugar
• Infection that is severe or involves the brain
• Liver failure
• Thyroid conditions that cause low thyroid hormone levels or very high thyroid hormone levels

Brain disorders or injury, such as:

• Dementia or Alzheimer's disease
• Head trauma
• Seizure
• Stroke

Injury or accidents, such as:

• Diving accidents and near drowning
• Heat stroke
• Very low body temperature (hypothermia)

Heart or breathing problems, such as:

• Abnormal heart rhythm (arrhythmia)
• Lack of oxygen (hypoxia) from any cause
• Low blood pressure (hypotension)
• Low sodium levels in the blood
• Severe heart failure
• Severe lung diseases
• Very high blood pressure

Toxins and drugs, such as:

• Alcohol abuse (binge drinking or damage from long-term alcohol use)
• Exposure to heavy metals, hydrocarbons, or toxic gases
• Overuse of drugs such as opiates, narcotics, sedatives, and anti-anxiety or seizure medications
• Side effect of almost any medicine, such as those used to treat seizures, depression, psychosis, and other illnesses

Get medical help for any decrease in consciousness, even when it is due to alcohol intoxication, fainting, or a seizure disorder that has already been diagnosed.

See the article on seizures for tips on how to care for a person who is having a seizure.

Persons with epilepsy or other seizure disorder should carry a Medic-Alert bracelet or pendant describing their condition. They should avoid situations that have triggered a seizure in the past.

Get medical help if someone has decreased alertness that cannot be explained. Call your local emergency number (such as 911) if normal alertness does not return quickly.

Most often, a person with decreased consciousness will be evaluated in an emergency room.

The doctor will perform a physical examination. The exam will include a detailed look at the heart, breathing, and nervous system.

The health care team will ask questions about the person's medical history and symptoms, including

• Time pattern
  • When did the decreased alertness happen?
  • How long did it last?
  • Has it ever happened before? If so, how many times?
  • Did the person behave the same way during past episodes?
• Medical history
  • Does the person have epilepsy or a seizure disorder?
  • Does the person have diabetes?
  • Has the person been sleeping well?
  • Has there been a recent head injury?
• Other
  • What medications does the person take?
  • Does the person use alcohol or drugs on a regular basis?
  • What other symptoms are present?

Tests that may be done include:

• Chest x-ray
• Complete blood count or blood differential
• CT scan or MRI of the head
• Electrocardiogram (ECG)
• Electroencephalogram (EEG)
• Electrolyte panel
• Toxicology panel
• Urinalysis

Treatment depends on the cause of the decreased alertness. How well a person does depends on the cause of the condition. The longer the person has had decreased alertness, the worse the outcome.

Blok BK, Newman TM. Syncope. In: Tintinalli JE, Kelen GD, Stapczynski JS, Ma OJ, Cline DM, eds. Emergency Medicine: A Comprehensive Study Guide. 6th ed. New York, NY: McGraw-Hill; 2004:chap 52.

Huff JS. Altered mental status and coma. In: Tintinalli JE, Kelen GD, Stapczynski JS, Ma OJ, Cline DM, eds. Emergency Medicine: A Comprehensive Study Guide. 6th ed. New York, NY: McGraw-Hill; 2004:chap 259.

Kirsch TD. Head injury. In: Tintinalli JE, Kelen GD, Stapczynski JS, Ma OJ, Cline DM, eds. Emergency Medicine: A Comprehensive Study Guide. 6th ed. New York, NY: McGraw-Hill; 2004:chap 255.

Huff JS, Martin ML. Altered mental status and coma. In: Wolfson AB, Hendey GW, Ling LJ, et al, eds. Harwood-Nuss' Clinical Practice of Emergency Medicine. 5th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2009:chap 14.