The tilt-table test typically evokes the attack. Avoiding what brings on the syncope and possibly greater salt intake is often all that is needed.Associated symptoms may be felt in the minutes leading up to a vasovagal episode and are referred to as the prodrome. These consist of light-headedness, confusion, pallor, nausea, salivation, sweating, tachycardia, blurred vision, and sudden urge to defecate among other symptoms.Vasovagal syncope can be considered in two forms:

Isolated episodes of loss of consciousness, unheralded by any warning symptoms for more than a few moments. These tend to occur in the adolescent age group and may be associated with fasting, exercise, abdominal straining, or circumstances promoting vaso-dilation (e.g., heat, alcohol). The subject is invariably upright. The tilt-table test, if performed, is generally negative. Recurrent syncope with complex associated symptoms. This is neurally mediated syncope (NMS). It is associated with any of the following: preceding or succeeding sleepiness, preceding visual disturbance ("spots before the eyes"), sweating, lightheadedness. The subject is usually but not always upright. The tilt-table test, if performed, is generally positive. It is relatively uncommon.Syncope has been linked with psychological triggers. This includes fainting in response to the sight or thought of blood, needles, pain, and other emotionally stressful situations. One theory in evolutionary psychology is that fainting at the sight of blood might have evolved as a form of playing dead which increased survival from attackers and might have slowed blood loss in a primitive environment. "Blood-injury phobia", as this is called, is experienced by about 15% of people.
Symptoms include deep and fast respiration, weak and slow pulse, and respiratory pauses that may last for 60 seconds. Subclavian steal syndrome arises from retrograde (reversed) flow of blood in the vertebral artery or the internal thoracic artery, due to a proximal stenosis (narrowing) and/or occlusion of the subclavian artery. Symptoms such as syncope, lightheadedness, and paresthesias occur while exercising the arm on the affected side (most commonly the left). Aortic dissection (a tear in the aorta) and cardiomyopathy can also result in syncope.Various medications, such as beta blockers, may cause bradycardia induced syncope.A pulmonary embolism can cause obstructed blood vessels and is the cause of syncope in less than 1% of people who present to the emergency department. Blood pressure
Orthostatic (postural) hypotensive syncope is caused primarily by an excessive drop in blood pressure when standing up from a previous position of lying or sitting down. When the head is elevated above the feet the pull of gravity causes blood pressure in the head to drop. This is sensed by stretch receptors in the walls of vessels in the carotid sinus and aortic arch. These receptors then trigger a sympathetic nervous response to compensate and redistribute blood back into the brain. The sympathetic response causes peripheral vasoconstriction and increased heart rate. These together act to raise blood pressure back to baseline. Apparently healthy individuals may experience minor symptoms ("lightheadedness", "greying-out") as they stand up if blood pressure is slow to respond to the stress of upright posture.