Step 1: What is Blood Pressure?   Next Page

Every time your heart beats, it pushes blood out to your entire body. The blood moves through blood vessels called arteries. The term blood pressure refers to how hard the blood is pressing against the walls of your arteries.

When your heart contracts, blood is forced out of the heart, and the pressure increases. When your heart relaxes, the pressure decreases.

A blood pressure monitor allows you to see the pressure at both points. The higher number is called the systolic pressure, and the lower number is the diastolic pressure. For example, a normal blood pressure is "115 over 70":

115 systolic pressure (heart contracting)
70 diastolic pressure (heart relaxing)

What is "high" blood pressure?

High blood pressure, or "hypertension," often has no obvious cause, although many factors can contribute. When you have high blood pressure, your blood vessels are too narrow or they have too much blood circulating in them. High blood pressure puts a strain on blood vessels throughout your body and increases the workload on the heart. The result is that one or both of those numbers is higher than it should be.

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What should my numbers be?

The chart below shows how blood pressure is classified in adults at least 18 years old. You want your blood pressure reading to be lower than "120 over 80."

  Systolic Diastolic
Normal Less than 120 Less than 80
Pre-High blood pressure 120-139 80-89
High Blood Pressure -
Stage 1
140 - 159 90 - 99
High Blood Pressure -
Stage 2
160 or over 100 or over

It's possible for only ONE of the numbers to be high (the systolic or diastolic). It is particularly important to keep an eye on a high systolic number.

Learn More

Pay Attention to Your Systolic Pressure!

To continue to the next step of the high blood pressure guide, click "next" below.


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Review Date: June 3, 2003

Reviewed By: Jacqueline A. Hart, M.D., Department of Internal Medicine, Newton-Wellesley Hospital, Harvard University and Senior Medical Editor, A.D.A.M., Inc.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2004 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

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