A tilt table test is a diagnostic test used to help a physician determine why a patient has been experiencing dizziness, lightheadedness or fainting spells (syncope). There are a number of different factors that may cause fainting spells, and the tilt table test is used to assess one in particular – a sudden drop in blood pressure (due to a widening of the blood vessels), often with a drop in heart rate as well. Fainting that results from this change in blood pressure and blood vessels is now called neurocardiogenic syncope, although many people still refer to the syndrome as vasovagal syncope.

Neurocardiogenic syncope often occurs after an event that causes emotional stress. It may also be provoked by dehydration or by standing upright for a prolonged period of time. Normally, stress increases the amount of adrenaline released by the body and causes the heart rate to speed up. However, stress may trigger a reflex in certain people that causes a sudden slowing of the heartbeat and a dangerous drop in blood pressure, leading to fainting.

Fainting may also result from other causes of low blood pressure, such as orthostatic hypotension or neurogenic orthostatic hypotension. These conditions are characterized by the body's inability to quickly regulate blood pressure, especially when standing up quickly or after other abrupt changes in position. When a person stands, gravity causes blood to pool in the leg vein, reducing the amount of blood that returns to the heart. Normally, the autonomic nervous system adapts by constricting the blood vessels and increasing the heart rate. If this process does not work properly, blood pressure can drop causing a feeling of lightheadedness and possible fainting.

A tilt table test may also be recommended to individuals who do not experience fainting, but who have the need to lie down as a result of feeling lightheaded.