[2] Severely low blood pressure can deprive the brain and other vital organs of oxygen and nutrients, leading to a life-threatening condition called shock.

[19][20] For many people, excessively low blood pressure can cause dizziness and fainting or indicate serious heart, endocrine or neurological disorders.

[4] For some people, low blood pressure may be a sign of an underlying health condition, especially when it drops suddenly or occurs with symptoms.

[5] Older adults also have a higher risk of symptoms of low blood pressure, such as falls, fainting, or dizziness when standing or after a meal.

[16] Low blood pressure may also be attributed to heat stroke which can be indicated by absence of perspiration, light headedness and dark colored urine.

[29] This can be due to decreased sympathetic nervous system output or to increased parasympathetic activity occurring as a consequence of injury to the brain or spinal cord.

[39] Simple blood pressure and heart rate measurements while lying, seated, and standing (with a two-minute delay in between each position change) can confirm the presence of orthostatic hypotension.

[40] Vasovagal syncope is a form of dysautonomia characterized by an inappropriate drop in blood pressure while in the upright position.

[18] Vasovagal syncope occurs as a result of increased activity of the vagus nerve, the mainstay of the parasympathetic nervous system.

[18] Patients will feel sudden, unprovoked lightheadedness, sweating, changes in vision, and finally a loss of consciousness.

[41] Another, but rarer form, is postprandial hypotension, a drastic decline in blood pressure that occurs 30 to 75 minutes after eating substantial meals.

[42] Postprandial hypotension is believed to be caused by the autonomic nervous system not compensating appropriately, because of aging or a specific disorder.

[42] Hypotension is a feature of Flammer syndrome, which is characterized by cold hands and feet and predisposes to normal tension glaucoma.

[20] Hypotension can be a symptom of relative energy deficiency in sport, sometimes known as the female athlete triad, although it can also affect men.

[2] The vast and rapid compensation abilities of the autonomic nervous system allow normal individuals to maintain an acceptable blood pressure over a wide range of activities and in many disease states.

[5] However, occasional blood pressure readings below 90/60 mmHg are not infrequent in the general population,[46] and, in the absence of some pathological cause, hypotension appears to be a relatively benign condition in most people.

[46] The diagnosis of hypotension is usually made by measuring blood pressure, either non-invasively with a sphygmomanometer or invasively with an arterial catheter (mostly in an intensive care setting).

In mild cases, where the patient is still responsive, laying the person on their back and lifting the legs increases venous return, thus making more blood available to critical organs in the chest and head.

The clinical history provided by the caretaker is the most important part in determining the cause of hypotension in pediatric patients.