Blood pressure refers to the pressure of blood in your blood vessels. Blood pressure is measured in millimetres of mercury (mm Hg) and is recorded as two figures. For example blood pressure may be recorded at 140/90 mm Hg, which is referred to as 140 over 90.
- The top (first) number is the systolic pressure, which is the pressure in the arteries when the heart contracts.
- The bottom (second) number is the diastolic pressure, which is the pressure in the arteries when the heart rests between each heartbeat.