Your blood pressure is recorded as two numbers. The systolic blood pressure (the
“upper” number) tells how much pressure blood is exerting against your artery walls
while the heart is pumping blood. The diastolic blood pressure (the “lower” number)
tells how much pressure blood is exerting against your artery walls while the heart is
resting between beats. Blood pressure is measured in units of millimeters of mercury, or
mm Hg. For example, a blood pressure reading might be 120/80 mm Hg.