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 or 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 the question suggest a change in mental status.
Loss of consciousness - first aid; Coma - first aid; Mental status change; Altered 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.
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 (vasovagal syncope), coughing very hard, or breathing very fast (hyperventilating).
The person will be unresponsive (does not respond to activity, touch, sound, or other stimulation).
The following symptoms may occur after a person has been unconscious:
Amnesia for events prior to, during, and even after the period of unconsciousness
Check the person's airway, breathing, and pulse frequently. If necessary, begin rescue breathing and CPR.
If the person is breathing and lying on the back, and you do not think there is a spinal injury, carefully roll the person toward you onto the side. Bend the top leg so both hip and knee are at right angles. Gently tilt the head back to keep the airway open. If breathing or pulse stops at any time, roll the person on to his back and begin CPR.
If you think there is a spinal injury, leave the person where you found them (as long as breathing continues). If the person vomits, roll the entire body at one time to the side. Support the neck and back to keep the head and body in the same position while you roll.
Keep the person warm until medical help arrives.
If you see a person fainting, try to prevent a fall. Lay the person flat on the floor and raise the feet about 12 inches.
If fainting is likely due to low blood sugar, give the person something sweet to eat or drink when they become conscious.
Do NOT give an unconscious person any food or drink.
Do NOT leave the person alone.
Do NOT place a pillow under the head of an unconscious person.
Do NOT slap an unconscious person's face or splash water on the face to try to revive him.
When to Contact a Medical Professional
Call 911 if the person is unconscious and:
Does not return to consciousness quickly (within a minute)
Has fallen down or been injured, especially if bleeding
Has lost bowel or bladder control
Is not breathing
Is over age 50
Call 911 if the person regains consciousness but:
Feels chest pain, pressure, or discomfort, or has a pounding or irregular heartbeat
Can't speak, has vision problems, or can't move the arms and legs
Jacob L. Heller, MD, MHA, Emergency Medicine, Virginia Mason Medical Center, Seattle, Washington. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.