Dysautonomia is an encompassing term used to describe any dysfunction of the Autonomic Nervous System (ANS), both Sympathetic and Parasympathetic divisions. The ANS is the part of the nervous system that regulates everything that happens in the body automatically, without cognitive thought, such as: respiration, swallowing, heart rate/blood pressure, dilation/constriction of pupils, organ function (including the stomach and intestines that work together for digestion), metabolism, temperature control (ability to sweat/shiver), the creation of bodily fluids (sweat, saliva and tears), the creation/release of chemicals and chemical reactions, sexual responses, etc. Dysautonomia is most common amongst those with damage done to the brainstem or Vagus Nerve.

Examples of Diagnoses of Dysautonomia include: Postural Orthostatic Tachycardia Syndrome (POTS), Neurocardiogenic Syncope (NCS) and Multiple System Atrophy (MSA).

A form of dysautonomia.  Often abbreviated as POTS, it is an abnormal increase in heart rate upon standing.   POTS is diagnosed by a tilt table test, or prolonged standing test, and a test is considered positive for POTS when an adult experience an increase in heart rate of 30 beats per minute within ten minutes of standing (or 40 bpm for an adolescent), or if the heart rate reaches 120 or above.  A diagnosis also requires that a patient experiences symptoms such as lightheadedness, syncope (fainting), shakiness, fatigue, anxiety, nausea, vomiting, sweating and fatigue.