Syncope is the medical term for fainting or passing out. It is caused by a temporary drop in the amount of blood that flows to the brain. This leads to loss of consciousness and muscle control. The person then falls down or over, which allows blood flow to return to the brain. Returning blood flow allows the person to regain consciousness, although feeling confused for a bit. Syncope usually lasts only seconds or minutes.

For most people, syncope occurs once in a great while, if ever, and is not a sign of serious illness. However in others, syncope can be the first and only warning sign prior to an episode of sudden cardiac death. Syncope can also lead to serious injury.

Pre-syncope is the feeling that you are about to faint. Someone with pre-syncope may be lightheaded (dizzy) or nauseated, have a visual "gray out" or trouble hearing, have palpitations, or feel weak or suddenly sweaty.

Types of Syncope

Becoming unconscious due to a seizure, heart attack, head injury, stroke, intoxication, blow to the head, diabetic hypoglycemia or other emergency condition is not considered syncope.


Common symptoms of syncope in addition to fainting include:


It's important to identify the cause of syncope, if possible, to rule out a dangerous heart condition. Depending on your symptoms and circumstances, the following tests may be used to find the cause: