Blood pressure measurement
Blood pressure is a measurement of the force on the walls of your arteries as your heart pumps blood through your body.
You can measure your blood pressure at home. You can also have it checked at your health care provider’s office or even a fire station.
Diastolic blood pressure; Systolic blood pressure; Blood pressure reading; Measuring blood pressure; Hypertension - blood pressure measurement; High blood pressure - blood pressure measurement
How the Test is Performed
Sit in a chair with your back supported. Your legs should be uncrossed, and your feet on the floor.
Your arm should be supported so that your upper arm is at heart level. Roll up your sleeve so that your arm is bare.
You or your provider will wrap the blood pressure cuff snugly around your upper arm. The lower edge of the cuff should be 1 inch (2.5 cm) above the bend of your elbow.
- The cuff will be inflated quickly. This is done either by pumping the squeeze bulb or pushing a button on the device. 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 stops is recorded. This is the diastolic pressure.
Inflating the cuff too slowly or not inflating it to a high enough pressure may cause a false reading. If you loosen the valve too much, you will not be able to measure your blood pressure.
The procedure may be done two or more times.
How to Prepare for the Test
Before you measure your blood pressure:
- Rest for at least 5 minutes, 10 minutes is better, before blood pressure is taken.
- DO NOT take your blood pressure when you are under stress, have had caffeine or used tobacco in the past 30 minutes, or have exercised recently.
Take 2 or 3 readings at a sitting. Take the readings 1 minute apart. Remain seated. When checking your blood pressure outside the doctor’s office, note the time of the readings. Your provider may suggest that you do your readings at certain times.
- You may want to take your blood pressure in the morning and at night for a week.
- This will give you at least 14 readings and will help your provider 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
High blood pressure has no symptoms so you may not know if you have this problem. High blood pressure is often discovered during a visit to the provider for another reason.
Finding high blood pressure and treating it early can help prevent heart disease, stroke, eye problems, or chronic kidney disease. All adults 18 years and older should have their blood pressure checked regularly:
- Once a year for adults aged 40 years and older
- Once a year for persons at increased risk for high blood pressure, including people who are overweight or obese, African Americans, and those with high-normal blood pressure 130 to 139/85-89 mm Hg
- Every 3 to 5 years for adults aged 18 to 39 years with blood pressure lower than 130/85 mm Hg who do not have other risk factors
Your provider may recommend more frequent screenings based on your blood pressure levels and other health conditions.
Blood pressure readings are usually given as two numbers. For example, your provider might tell you that your blood pressure is 120 over 80 (written as 120/80 mm Hg). 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 mm Hg).
What Abnormal Results Mean
High blood pressure (hypertension) is when the top number (systolic blood pressure) is 140 mm Hg or more most of the time or the bottom number (diastolic blood pressure) is 90 mm Hg or more most of the time (written as 140/90 mm Hg).
If your blood pressure numbers are 120/80 mm Hg or higher but below 140/90 mm Hg, it is called pre-hypertension. If you have pre-hypertension, you are more likely to develop high blood pressure.
If you have diabetes, heart disease, or kidney problems, or if you had a stroke, your provider may want your blood pressure to be lower.
The most commonly used blood pressure targets for people with these medical problems are below 130 to 140/80 mm Hg.
Most of the time, high blood pressure does not cause symptoms.
It is normal for your blood pressure to vary at different times of the 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 provider’s office.
- Make sure your home blood pressure monitor is accurate.
- Ask your provider to compare your home readings with those taken in the office.
Many people get nervous at the provider’s office and have higher readings than they have at home. This is called white coat hypertension. Home blood pressure readings can help detect this problem.
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Reviewed By: Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.