Systolic blood pressure refers to the pressure of blood in the artery when the heart contracts. It is the top (and higher) number in a blood pressure reading.
Diastolic blood pressure refers to the pressure of blood in the artery when the heart relaxes between beats. It is the bottom (and lower) number in a blood pressure reading.
For example, if a person's systolic pressure is 120 millimetres of mercury (mm Hg) and the diastolic pressure is 80 mm Hg, blood pressure is recorded as 120/80 and read as "120 over 80."
Last Revised: May 30, 2013
Author: Healthwise Staff
Medical Review: E. Gregory Thompson, MD - Internal Medicine & Brian D. O'Brien, MD - Internal Medicine & Robert A. Kloner, MD, PhD - Cardiology
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