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Apr 11, 2024

Monitoring blood pressure at home? Make sure you follow these steps

Staying Healthy When was the last time you had your blood pressure checked? All adults should have this simple test at least once a year. If a blood pressure reading at your doctor's office is

Staying Healthy

When was the last time you had your blood pressure checked? All adults should have this simple test at least once a year.

If a blood pressure reading at your doctor's office is elevated — that is, higher than a healthy range — current guidelines from the US Preventive Services Task Force recommend repeating the measurement outside of a clinic setting before starting treatment. But that's not the only reason why your doctor may suggest regularly tracking your blood pressure at home.

"Some people have blood pressure elevations only at the doctor's office, which is known as white-coat hypertension," says Dr. Stephen Juraschek, associate professor of medicine at Harvard-affiliated Beth Israel Deaconess Medical Center. One of the best ways to know if your blood pressure is truly higher than normal is to measure it multiple times at home.

Home monitoring is also a good idea:

Very basic models cost as little as $25. But more expensive models, which range from about $50 to $100, may be more convenient to use. They can store multiple readings and send the data to your computer or smartphone — or even directly to the patient portal at your doctor's office.

Home blood pressure monitoring is a bit more involved than some people assume. "It's not something you just do sporadically or whenever you have time," says Dr. Juraschek.

Ask your doctor how often and what time of day to take your blood pressure.

"The gold standard for home monitoring is to take 28 separate measurements, which you can then average to get a representative reading," says Dr. Juraschek.

That means taking your blood pressure four times a day — twice in the morning and twice in the evening — for seven days in a row. However, even 12 measurements over three days is reasonable, especially if you include one weekend day, Dr. Juraschek says. Your doctor can advise you about what makes the most sense for your situation.

Common mistakes can raise your blood pressure reading by a few points, or as much as 10 or even up to 25 points in some cases. Here's what to do or avoid — and why — for an accurate blood pressure reading.

Why? Caffeine and nicotine constrict blood vessels and boost your heart rate, which can raise blood pressure. Alcohol dilates blood vessels, possibly lowering blood pressure. And exercise increases heart rate and blood pressure.

Why? A full bladder can put pressure on and reduce blood flow to your kidneys. Your body's natural response is to raise your blood pressure to make sure your kidneys are getting enough blood.

Sit back in your chair with your feet flat on the floor, legs and ankles uncrossed, and your arm extended, palm up, on a table so that your elbow is positioned roughly at heart height.

Why? Crossing your legs, especially at the knee, temporarily raises blood pressure. If your feet or your arm are not supported, your muscles will contract. Even this small amount of isometric exercise can raise your blood pressure. Also, supporting your arm below or above the level of your heart may affect the accuracy of the reading.

First, wrap the proper size cuff around your bare arm about an inch above the crook of your elbow. Sit quietly for a few minutes without distractions like TV, reading, phone scrolling, or talking. Then start the machine to take your blood pressure.

Why? Putting the cuff over clothes — or pushing up your sleeve so that it's tight around your upper arm — may interfere with an accurate reading, though evidence on this is mixed. Ideally, you want to record blood pressure while feeling relaxed, not distracted, because even minor stress or tension can raise your blood pressure.

This video from the American Heart Association demonstrates the correct technique.

Nearly half of all adults have high blood pressure, but about a third of these people aren't even aware they have the problem. An accurate diagnosis and treatment is vital, says Dr. Juraschek. Few things in medicine have shown such consistent results as the harms of high blood pressure, which is a major cause of heart attacks, strokes, kidney disease, and cognitive decline.

"It's called the silent killer for a reason. We don't feel or experience any of high blood pressure's effects until it's too late," he says.

Julie Corliss, Executive Editor, Harvard Heart Letter

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

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