Unconsciousness is when a person is unable to respond to people and activities. Often, this is called a coma or being in a comatose state.

Other changes in awareness can occur without becoming unconscious. Medically, these are called "altered mental status" or "changed mental status." They include sudden confusion, disorientation, or stupor.

Unconsciousness and any other SUDDEN change in mental status must be treated as a medical emergency.

If someone is awake but less alert than usual, ask a few simple questions, such as:

• What is your name?
• What is the date?
• How old are you?

Wrong answers or an inability to answer suggest a change in mental status.

Being asleep is not the same thing as being unconscious. A sleeping person will respond to loud noises or gentle shaking -- an unconscious person will not.

An unconscious person cannot cough or clear his or her throat. This can lead to death if the airway becomes blocked.

Unconsciousness can be caused by nearly any major illness or injury, as well as substance abuse and alcohol use.

Brief unconsciousness (or fainting) is often caused by dehydration, low blood sugar, or temporary low blood pressure. However, it can also be caused by serious heart or nervous system problems. Your doctor will determine if you need tests.

Other causes of fainting include straining during a bowel movement, coughing very hard, or breathing very fast (hyperventilating).

• Unresponsiveness (does not respond to activity, touch, or other stimulation)
• Confusion
• Light-headedness
• Rapid heart beat (palpitations)
• Headache
• Drowsiness
• Stupor