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Know Your Blood Pressure Numbers

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Often wonder what the top and the bottom blood pressure numbers mean? Doctors call them systolic (the top number) and diastolic (the bottom number) blood pressure.

Knowing both your systolic and diastolic blood pressure numbers is important and could save your life. 

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What Does the Systolic Blood Pressure Number Mean?

When your heart beats, it contracts and pushes blood through the arteries to the rest of the body. This force creates pressure on the arteries. This is called systolic blood pressure.

A normal systolic blood pressure is below 120.

A systolic blood pressure of 120 to 139 means you have prehypertension, or borderline high blood pressure. Even people with prehypertension are at a higher risk of developing heart disease.

A systolic blood pressure number of 140 or higher is considered to be hypertension, or high blood pressure.

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.

A normal diastolic blood pressure number is less than 80.

A diastolic blood pressure between 80 and 89 indicates prehypertension.

A diastolic blood pressure number of 90 or higher is considered to be hypertension or high blood pressure.

How Is Blood Pressure Measured?

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.

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).

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