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Getting your blood pressure checked at the doctor’s office is so common that most people don’t pay much attention when it’s done—but they should. According to the American Heart Association (AHA), some patients may be told that they have high blood pressure when they really don’t.

The problem is, many healthcare professionals—doctors, nurses, physician assistants, and others—don’t follow all the steps needed to get an accurate reading. Whether they don’t know these best practices or are in a hurry, the result is the same: you may get inaccurate readings that are too high.

“These simple things can make a difference in whether or not a person is classified as having high blood pressure that requires treatment,” said Michael Hochman, MD, MPH, in an AHA news release.

Here’s what to know so this won’t happen to you.

Why high blood pressure matters

Having high blood pressure (also called hypertension) means there’s too much pressure in the vessels that carry blood through your body. It’s alarmingly common. Under current AHA guidelines, nearly half of all adults in the United States have high blood pressure.

There are usually no symptoms until high blood pressure causes serious complications such as a heart attack or stroke. That’s why it’s important to check your blood pressure regularly so these problems can be prevented. Simple treatments are generally very effective.

But only if you really need them.

Avoiding measurement mistakes

The AHA names seven common blood pressure measurement mistakes that could lead to artificially high readings:

  • Failure to have the patient sit quietly for about five minutes before the measurement
  • Placing the blood pressure cuff over clothing instead of a bare arm
  • Using a cuff that is too small
  • Talking with the patient during the measurement, or letting them talk on their phone
  • Not having the patient visit the bathroom: a full bladder can raise the reading significantly
  • Not having the patient sit correctly: He or she should sit in a chair with back support and place both feet flat on the floor or a footstool. Legs should be uncrossed.
  • Arm position: the cuffed arm shouldn’t dangle or be held up during the reading; rest it on a table or counter so the cuff is level with the heart

When 30 clinicians and other healthcare professionals were recently tested on their blood pressure measurement techniques, only three of them did everything right. If the person who’s taking your reading doesn’t follow all the right steps, politely speak up.

You also need to do a few things on your own. In the 30 minutes before blood pressure is taken, you shouldn’t smoke, consume caffeine, or exercise.

Everything was done correctly, but my reading is high!

Don’t panic over a single high measurement. Blood pressure normally fluctuates for a variety of reasons. Being diagnosed with high blood pressure requires more than one high reading, taken on separate occasions. Talk with your clinician about follow-up visits.

The common mistakes listed above are just as important when you’re checking blood pressure at home. “Knowing how to measure blood pressure accurately at home, and recognizing mistakes in the physician’s office, can help you manage your pressure and avoid unnecessary medication changes,” says Hochman.

Bonus tip: white coat hypertension

Some people have higher blood pressure in the doctor’s office than they normally do at home, even if their blood pressure is measured correctly following the recommendations above. This is called “white coat hypertension” because healthcare providers often wear white coats. It may be linked to the stress or anxiety people sometimes feel when seeing the doctor.

White coat hypertension was once thought to be harmless, but now some experts say it may be a sign of an underlying problem. If you have white coat hypertension, talk with your doctor about the best way to get reliable blood pressure readings.

Do you have high blood pressure? Add a comment below to tell us how you’re doing, and which treatments helped (or didn’t).