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Blood pressure measurement

Definition

Blood pressure is a measurement of the force applied to the walls of your arteries as your heart pumps blood through your body.

Your blood pressure can be measured at home, or at your health care provider's office, a fire station, pharmacies, and many other places.

Alternative Names

Diastolic blood pressure; Systolic blood pressure; Blood pressure reading; Measuring blood pressure

How the test is performed

Your arm should be supported, with your upper arm at heart level, back supported, legs uncrossed, and feet on the floor. Your upper arm should be bare, with your sleeve comfortably rolled up.

You or your health care provider will wrap the blood pressure cuff snugly around your upper arm. The lower edge of the cuff should be 1 inch above the bend of your elbow.

  • The cuff will be inflated quickly, either by pumping the squeeze bulb or pushing a button. You will feel tightness around your arm.
  • Next, the valve of the cuff is opened slightly, allowing the pressure to slowly fall.
  • As the pressure falls, the reading when the sound of blood pulsing is first heard is recorded. This is the systolic pressure.
  • As the air continues to be let out, the sounds will disappear. The point at which the sound disappears is recorded. This is the diastolic pressure.

Inflating the cuff too slowly or not high enough may cause a false reading. If you loosen the valve too much, you won't be able to determine your blood pressure.

The procedure may be done two or more times.

How to prepare for the test

Measuring your blood pressure is best done after you rest for at least 5 minutes.

Do not take your blood pressure when you're under stress, have consumed caffeine or used a tobacco product in the past 30 minutes, or have recently exercised.

Take two or three readings at a sitting, 1 minute apart, while resting in a seated position. When measuring your blood pressure outside of a medical office, it is important to note the time of the readings.

Your doctor may suggest that you do your readings at certain times. A common recommendation is to take your blood pressure in the morning and at night for a week. That way, you will get at least 12 readings to help your doctor make decisions about your blood pressure treatment.

How the test will feel

You will feel slight discomfort when the blood pressure cuff is inflated to its highest level.

Why the test is performed

Because there are no symptoms, you can have high blood pressure and not know it. High blood pressure may be found when you visit your health care provider for other reasons.

Diagnosing high blood pressure early can help prevent heart disease, stroke, eye problems, or chronic kidney disease.

All adults should have their blood pressure checked every 2 years, if their blood pressure was less than 120/80 mmHg at the most recent reading. You should have it checked yearly if your last reading was 120-139/80-89 mm Hg.

If you have high blood pressure, diabetes, heart disease, kidney problems, or certain other conditions, you should have your blood pressure checked more often -- at least every year.

Normal Values

Blood pressure readings are usually given as two numbers -- for example, 120 over 80 (written as 120/80 mmHg). One or both of these numbers can be too high.

Normal blood pressure is when the top number (systolic blood pressure) is below 120 most of the time, and the bottom number (diastolic blood pressure) is below 80 most of the time (written as 120/80 mmHg).

If your blood pressure numbers are 120/80 or greater but below 140/90, it is called pre-hypertension. If you have pre-hypertension, you are more likely to develop high blood pressure.

What abnormal results mean

High blood pressure (hypertension) is when the top number (systolic blood pressure) is 140 or more most of the time or the bottom number (diastolic blood pressure) is 90 or more most of the time. (written as 140/90 mmHg).

If you have diabetes, heart disease, or kidney problems, or if you had a stroke, your doctor may want your blood pressure to be lower.

Most of the time, high blood pressure does not cause symptoms. For most patients, high blood pressure is found when they visit their health care provider or have it checked elsewhere.

See also: Preeclampsia to learn about high blood pressure in pregnant women.

Special considerations

It is normal for your blood pressure to be different depending on the time of day:

  • It is usually higher when you are at work.
  • It drops slightly when you are at home.
  • It is usually lowest when you are sleeping.
  • It is normal for your blood pressure to increase suddenly when you wake up. In people with very high blood pressure, this is when they are most at risk for a heart attack and stroke.

Blood pressure readings taken at home may be a better measure of your current blood pressure than those taken at your doctor's office, as long as you make sure your machine is accurate. You can ask your health care provider to compare your home readings with those taken in the office.

Many people become nervous at the doctor's office and have higher readings than they normally would at home. This is called white coat hypertension.

References

Victor RG. Systemic hypertension: Mechanisms and diagnosis. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 45.

Victor RG. Arterial hypertension. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 67.


Review Date: 5/28/2012
Reviewed By: David C. Dugdale, III, MD, professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, 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 medical professional 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. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
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