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Off the cuff: Measuring blood pressure

High blood pressure may not cause symptoms, so it's important to know your levels.

You know the drill: You extend your arm, the doctor or nurse wraps a cuff around it, and your blood pressure is checked.

But how does everything work—the cuff, valve, gauge and numbers? And what's the big deal about blood pressure anyway?

The silent killer

You can't necessarily feel high blood pressure, but don't let that deceive you. Hypertension—a consistent blood pressure level of 130/80 mm Hg or higher—can take a life-threatening toll on your blood vessels, heart and brain for years without causing any symptoms. That's why high blood pressure is often called the silent killer.

The only way to find out whether you have hypertension is to have your blood pressure checked.

How it's checked

Blood pressure is typically checked with a sphygmomanometer—the tongue-twisting name for the cuff and gauge.

The test is quick and easy: A cuff is wrapped around your upper arm and inflated. The cuff compresses a large artery in the arm, stopping blood flow for a few seconds.

Next, a valve lets some air out of the cuff and blood starts to flow again. Meanwhile, a stethoscope is used to listen for the sound of blood rushing back through the artery.

The first thumping sound that's heard is the systolic blood pressure—the force of blood in the arteries when your heart beats. This is the first number in your blood pressure reading.

When the thumping sound is no longer heard, that's the diastolic pressure—the force of blood in the arteries between beats, when your heart rests. This is the second number in your reading.

Both numbers are important, according to the American Heart Association (AHA). As we get older, systolic blood pressure is especially important.

For accuracy

To help ensure an accurate blood pressure reading:

  • Do not drink coffee or smoke cigarettes 30 minutes before the test.
  • Sit for five minutes with your back supported and your feet flat on the ground right before the test. Rest your arm on a table at the level of your heart.
  • Wear short sleeves so your arm is exposed.
  • Go to the bathroom prior to the reading. A full bladder can change your blood pressure reading.
  • After the test, ask the doctor or nurse to tell you your blood pressure level in numbers.

Numbers to shoot for

With blood pressure, lower numbers are generally better. As the numbers rise, so do the risks.

  • Blood pressure lower than 120/80 is considered normal and healthy.
  • Blood pressure of 120-129 systolic and less than 80 diastolic is considered elevated. People who have blood pressure within this range are more likely to end up with high blood pressure unless they take action to prevent it, according to the AHA.
  • Blood pressure of 130 or higher systolic or 80 or higher diastolic is considered hypertension.

Talk with your doctor about what your target blood pressure should be. Those with diabetes may have different treatment goals, according to the American Diabetes Association.

Several readings may be taken over time to determine whether a person has high blood pressure.

At home and away

Blood pressure can be checked at home too. Measuring devices can be purchased at various places, such as discount stores and pharmacies.

There are several options, including the familiar blood pressure cuff and stethoscope, or devices with digital readouts. Your doctor, nurse or pharmacist can recommend a good device and show you how to use it.

Finally, a word about the electronic blood pressure monitors you may see in supermarkets and drugstores.

These machines may be convenient, but they may not give very accurate results, according to the U.S. Department of Health and Human Services. Electronic blood pressure monitors should not be used as a substitute for sphygmomanometer readings.

If you'd like more information on how and when to check your blood pressure, talk with your doctor.

Reviewed 3/3/2023

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