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Is your blood pressure really high or are you taking it wrong? How to improve readings.

Along with the holidays come time-honored dishes like ham, stuffing, gravy and green bean casserole.

Since much of that good food often comes with a lot of sodium, the holidays are a good time for the 120 million U.S. adults managing high blood pressure to take extra precautions and monitor themselves to ensure they're maintaining normal levels.

The problem for people with hypertension is getting an accurate reading.

Studies show blood pressure readings are not always accurate or consistent outside of the medical setting. They vary widely depending on who’s taking measurements, where and when they're being taken, and what type of medical device is being used.

Disparate readings can also happen in medical settings.

Unreliable readings can have life-threatening consequences for patients trying to manage high blood pressure, which is a major risk factor for heart disease – the leading cause of death in the country.

“We’ve been too casual about how we’re taking blood pressure both at home and the office,” said Dr. Harlan Krumholz, cardiologist and director of Yale University’s Center for Outcomes Research and Evaluation. “We need to get rid of some of this noise in the measurements.”

Measuring blood pressure

Blood pressure is measured using two numbers.

Systolic blood pressure is the top number and measures the pressure in your arteries when your heart beats, according to the Centers for Disease Control and Prevention. Diastolic blood pressure measures the pressure in your arteries when your heart rests between beats.

Patients can get widely varied readings from different providers, depending on what monitors they're using and how they're using them.

A March study through the Yale New Haven Health System looked at 7.7 million blood pressure measurements in more than 530,000 adults and found a wide variation in the readings. The difference between a single patient's readings averaged about 12 mm Hg, which is the difference between elevated blood pressure and stage 2 hypertension.

Among patients with extremely high blood pressure – above 180 mm Hg systolic – individuals' readings varied even more, on average 32.3 mm Hg, according to the study published in Circulation, the official journal of the American Heart Association.

The lack of consistency is a consequence of clinicians measuring blood pressure differently, experts say. Some use monitors with wrist cuffs rather than arm cuffs. Some place the cuff over that patient's clothes instead of putting it onto a bare arm. That all affects the blood pressure reading, Krumholz said.

“We should all be measuring it the same way, like a test, not willy-nilly where this clinic does it this way and this clinic does it that way – which is how it sort of happens now,” said Krumholz, who co-authored the Yale study.

Even the small matter of where and how the person being measured sits can impact a blood pressure reading. A September study found blood pressure readings taken with the patient on an exam table were higher by up to 7 mm Hg systolic and 4.5 mm Hg diastolic higher compared with measurements taken with a person seated in a chair.

A less-than-accurate reading could be the difference between a person having hypertension that requires medication and having elevated blood pressure that could be treated with nonpharmacological interventions, said study author Dr. Randy Wexler, a family physician at The Ohio State University Wexner Medical Center.

There's also a genuine concern about overdiagnosing people with high blood pressure, also called hypertension, when the problem is not genuinely acute.

“You’ve labeled somebody with a disease process they don’t have and that’s going to have potential implications for them,” he said.

What’s the best way to measure blood pressure?

While nearly anything could affect someone’s blood pressure, the AHA guidelines suggest these steps for getting the most accurate reading:

  • Don’t smoke, drink caffeinated beverages or exercise in the 30 minutes prior to taking a measurement

  • Relax for five minutes before taking a measurement

  • Make sure your bladder is empty and your blood pressure device is calibrated according to its directions

  • Use a cuff that fits on your bare arm, do not take measurements over clothing

  • Sit in an upright position with your back supported, feet flat on the floor and your arm supported on a table or stool at heart level

  • Do not talk while getting measured

Experts also recommend using a blood pressure monitor that has been approved by the American Medical Association.

For patients taking their blood pressure at home, Krumholz said consistency is key in monitoring changes. Take your blood pressure under the same circumstances during the same time of day every day, whether you are sitting down first thing in the morning or standing up right before bedtime. If possible, get multiple measurements and calculate the average.

What is considered high blood pressure?

The American College of Cardiology and the AHA published new guidelines for blood pressure management in 2017 that defined high hypertension as having a blood pressure reading of 130/80 mm Hg or higher.

The CDC says stage 2 hypertension is defined as a blood pressure at or above 140/90 mm Hg.

Hypertension puts a patient at risk for heart disease and stroke, the leading causes of death in the United States. In 2021, hypertension was a primary or contributing cause in nearly 700,000 U.S. deaths.

Send tips to Adrianna Rodriguez: adrodriguez@usatoday.com

Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.

This article originally appeared on USA TODAY: High blood pressure measurements aren't always accurate. Here's why.