The interruption in the blood supply to the brain that causes syncope may be experienced at first as lightheadedness, faintness, or dizziness. These warning signs before the loss of consciousness are known as presyncope. Other symptoms that may occur include blurred vision, nausea, weakness, and vertigo.

Syncope can be a serious problem because of the potential for personal injury due to falling or losing consciousness. This is especially significant for people who work in high-risk professions where loss of awareness may lead to serious accidents.