A New Study Says Arm Position Could Skew Blood Pressure Results—Here’s How to Take It Correctly

A recent Johns Hopkins University study found small details like where your arm is positioned or how you’re sitting could make a big difference in the accuracy of your blood pressure reading—and in some cases, even lead to a misdiagnosis of hypertension. To learn more, we spoke with Kieran Sheridan , a physiotherapist and founder of GulfPhysio. He shares what you should know about your readings and how to take your blood pressure properly at home.

How blood pressure is measured

First, let’s break down what’s happening when your doctor takes your blood pressure. “They use a tool named [a] sphygmomanometer—it is just a special name for an armband,” explains Sheridan.

“This is how it works: the cuff inflates around your upper arm to stop blood flow. When the cuff gradually loses air, a doctor or machine listens to hear blood flow returning into the artery,” he says. “The reading has two numbers: systolic pressure (the top number), when the heart beats, [and] diastolic pressure (the bottom number), when the heart takes a rest between each beat.”

According to Sheridan, a regular blood pressure reading is around 120/80 mmHg, measured in millimeters of mercury (mmHg).

How your arm position can affect blood pressure readings

Researchers at Johns Hopkins University conducted a trial with over 130 adults, measuring their blood pressure in three different scenarios using an automated device. The study, published in JAMA Internal Medicine on October 7, focused on how arm position during blood pressure screenings could skew the results.

In the first scenario, participants followed the recommended guidelines: their arm was supported on a desk, with the blood pressure cuff positioned at heart level. In the other two scenarios, participants' arms were either resting in their lap or hanging at their side—common positions that deviate from the proper protocol.

The trial found that when a participant’s arm rested in their lap, their systolic and diastolic blood pressure readings were four points higher. When their arm hung at their side, the systolic pressure jumped by 6.5 mmHg, and the diastolic by 4.4 mmHg. While these may seem like small differences, they’re enough to push someone from an “elevated” category into full-blown hypertension , explained more below.

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The risk of misdiagnosing hypertension

Hypertension , or high blood pressure, is often called the “silent killer” because it typically doesn’t have symptoms. Sheridan adds that as we age, watching for signs of hypertension matters. “High blood pressure can cause big health troubles like heart disease or strokes ,” he says.

Hypertension occurs from a systolic blood pressure of 130 mmHg or higher and a diastolic pressure of 80 mmHg or higher. For someone with a systolic reading of 128 mmHg—a number in the “elevated” range—a misplaced arm during the reading could push that number above 130, causing them to be misclassified as hypertensive.

“If doctors make mistakes and diagnose wrong, it can cause people to take medicines or get treatments they do not really need,” explains Sheridan. This is especially risky for older patients already managing multiple medications from various treatment plans.

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How to take your blood pressure at home

If you’re monitoring your blood pressure at home, getting an accurate reading is crucial. Below, Sheridan lays out some helpful tips for checking accurately:

Choose a time

“Blood pressure can change at different times of the day,” says Sheridan. “It is a good idea to check it at the same time each day, maybe in the morning when you wake up.”

Watch what you eat

“Eating food that has a lot of salt can make your blood pressure go up,” says Sheridan. Try to consume less sodium overall in your diet, and especially before measuring. “Also, avoid caffeine and smoking right before you take a reading,” she adds.

Position your body this way

“When you take your blood pressure, sit in a comfortable chair with [your] feet flat on the floor,” says Sheridan. It’s best to rest in this position for at least five minutes before taking a reading. Importantly, “keep your arm at heart level,” preferably on a table or flat surface. Then, wrap the cuff around your arm right above your elbow, making sure there’s skin contact.

Take several readings

“If the first reading shows high [results], wait a few minutes and try again. Sometimes I need little time to get an accurate number,” adds Sheridan. This ensures consistent results. Try to remain calm and quiet throughout each reading.

Whether you’re at the doctor’s office or taking blood pressure measurements at home, paying attention to your posture and arm position can make a big difference. “Do not be scared to ask questions when you visit a doctor or discuss with your family what you learn,” emphasizes Sheridan. “Keep finding out new information and take care of yourself!”

More on blood pressure:

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This content is not a substitute for professional medical advice or diagnosis. Always consult your physician before pursuing any treatment plan .