Also called postural hypotension, orthostatic hypotension is the abrupt fall in blood pressure that a person experiences when suddenly standing up from a sitting position, or while standing for long durations of time.

During sitting position or while standing for extended periods of time, blood accumulates in the lower extremities of the body.  This causes the autonomic nervous system to counteract the blood deficiency that occurs by pushing blood upward and supplying the brain with adequate oxygen. Apart from a properly functioning autonomic nervous system, this also depends on strong heart muscles to pump ample blood, blood vessels free from clots and blocks, and sufficient fluid content in the blood.

The symptoms of orthostatic hypotension are dizziness, lightheadedness, tunnel vision and often fainting. All these symptoms are due to the brain receiving inadequate amounts of blood.

Orthostatic hypotension can be caused by dehydration, which causes fluid levels in blood to drop, resulting in a decrease in the volume of blood, as well as anemia and blood loss. Medications such as diuretics (which increase the level of fluid excretion), beta blockers (which offset high blood pressure), antidepressants and sexual performance enhancers (such as Viagra).

There is no cure for orthostatic hypotension. However, taking lots of fluids and applying compressions on the lower extremities can help to alleviate the complications somewhat.