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Blood pressure (low)

Hypotension is persistent abnormally low blood pressure. Blood pressure is the pressure of blood in your arteries.

The blood circulation is a closed system in which the pressure varies constantly. It rises to a peak, called the systolic pressure, at the height of the contraction of each heartbeat.

Then it falls to a lower level, called the diastolic pressure, which it reaches just before each heartbeat. The diastolic pressure is the running pressure between beats.

Blood pressure varies between individuals and throughout the day. Blood pressure is normally above 90/60 mmHg.

Hypotension usually means blood pressure that is lower than 90/60 mmHg (millimeters of mercury) or is low enough to cause symptoms. When the blood pressure is too low there is inadequate blood flow to the brain and other vital organs, light-headedness or fainting may occur.

A common type of hypotension is postural (also known as orthostatic) hypotension, in which suddenly standing leads to light-headedness and fainting.

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