Fainting or syncope is a sudden (and generally momentary) loss of consciousness due to a lack of sufficient blood and oxygen reaching the brain. The first symptoms a person feels before fainting are dizziness and feeling hot. Moments later, the person's vision turns black and he or she drops to the floor (or slumps if seated in a chair).

Factors that influence fainting are taking in too little food and fluids, low blood pressure, physical exercise in excess of the energy reserve of the body, and lack of sleep. Even standing up too quickly or being in too hot a room can cause fainting.

Recommended treatment is to allow the person to lie on the ground with his or her legs a little elevated. As the dizziness and the momentary blindness passes, the person may experience visual disturbances in the form of small bright dots. These will also pass within a few minutes. If fainting happens frequently, or if there is no obvious explanation, it is important to see a doctor about it.

More serious causes of fainting include cardiac (heart-related) causes such as an abnormal heart rhythm (an arrhythmia), where the heart beats too slowly, too rapidly or too irregularly to pump enough blood to the brain. This can be life-threatening.

Fainting can also be due to neurological disorders, stress, etc.

See also

• orthostatic hypotension.