Syncope is a loss of consciousness (fainting) that occurs when blood pressure drops very low and not enough blood reaches the brain. A person may have shortness of breath, palpitations, or chest discomfort before fainting.

The reduction in blood flow usually happens quickly, which causes symptoms to appear suddenly.

Syncope can be caused by several conditions, such as dehydration, low blood volume, nervous system problems, heart problems, or a drop in blood pressure (orthostatic hypotension) when you move from a laying to standing position.

Syncope requires medical attention.