What Does the Diastolic Blood Pressure Number Mean?
The diastolic blood pressure number or the bottom number indicates the pressure in the arteries when the heart rests between beats. This is the time when the heart fills with blood and receives oxygen.
A normal diastolic blood pressure number is less than 80.
A diastolic blood pressure between 80 and 89 indicates prehypertension.
Blood pressure is measured with a simple, painless test using a blood pressure cuff -- doctors call it a sphygmomanometer. It consists of a small pressure gauge that is attached to a cuff.
The inflatable cuff is wrapped around your upper arm. Some blood pressure cuffs wrap around the forearm or wrist but often are not as accurate.
When measuring blood pressure, your doctor or nurse will use a stethoscope to listen to the blood moving through an artery.
The cuff is inflated to a pressure that’s known to be higher than your systolic blood pressure. As the cuff deflates, the first sound heard through the stethoscope is the systolic blood pressure. It sounds like a whooshing noise. When this noise goes away, that indicates the diastolic blood pressure.
The systolic blood pressure number is always said first, and then the diastolic blood pressure number is given. For example, your blood pressure may be read as "120 over 80" or written as 120/80.
Blood pressure is measured in millimeters of mercury (mm Hg).