How Body Position Can Lead to an Inaccurate Blood Pressure Reading

Blood pressure isn't a static number. Lots of things can cause it to fluctuate — your stress level, a cup of coffee, even fear of your doctor. Something as simple as how you're standing or sitting could cause your blood pressure to swing by 10 percent or more, according to Harvard Health Publishing.

However, an artificial shift in numbers upward can lead to a hypertension misdiagnosis if it puts you over the 130/80 reading that experts judge as borderline high blood pressure. If it swings in the other direction, your doctor could miss that you've developed high blood pressure.

So how do you get the most accurate read on whether your blood pressure is low, high or just right? Making sure you get the best measurement of this important health marker starts with being in the right position.

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There's an ideal way for your doctor to measure your blood pressure. "To get an accurate read on your blood pressure, sitting in a comfortable position with your feet on the ground after resting is the best option," says Suzanne Steinbaum, DO, a preventive cardiologist in New York City, co-author of ​Lower Your Blood Pressure Naturally​ and a spokesperson for the American Heart Association.

"Sit with your back straight and supported on a chair, for example. Your feet should be flat on the floor and your legs should not be crossed. Your arm should be supported on a flat surface, such as a table, with the upper arm at heart level. Make sure the bottom of the cuff is placed directly above the bend of the elbow," Dr. Steinbaum says.

Also, you shouldn't just rush in, sit down and have the doctor or nurse take your blood pressure reading. "One should be relaxed for at least five minutes prior to checking blood pressure," says Khadijah Breathett, MD, an assistant professor of cardiology at the University of Arizona Sarver Heart Center in Tucson.

Having your blood pressure taken while you're lying down, instead of sitting, can give you a slightly different number.

An August 2018 study with nearly 1,300 participants, published in the journal ​Medicine​, found that blood pressure measurements taken lying down were significantly lower than seated blood pressure measurements — and that discrepancy could result in doctors missing cases of high blood pressure.

In general, standing up while you're getting your blood pressure tested could increase your blood pressure reading. "The number upon standing can increase initially, especially if you change positions, causing a false diagnosis of high blood pressure," Dr. Steinbaum says.

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However, there's also a condition, called orthostatic or postural hypotension, that can develop if your blood pressure drops suddenly when you go from lying or sitting to standing, according to Harvard Health Publishing. If you feel a bit dizzy or lightheaded when you stand up, let your doctor know. "Large swings in blood pressure can be indicative of an ongoing disease," says Dr. Breathett.

For example, postural hypotension could go hand-in-hand with diabetes, Parkinson's disease or even cancer. A May 2018 study with more than 9,100 participants, published in the ​Journal of the American Heart Association​, found that people who developed postural hypotension were at greater risk of serious cardiovascular disease, including heart attack and stroke.

To determine if you have postural hypotension, your doctor will need to take two blood pressure readings: one when you've been sitting for five minutes and one after you've been standing for one to two minutes.

If you're curious in which position — sitting, lying down or standing — blood pressure is normally the highest, it's likely standing. But even if your numbers are high, your doctor may encourage you to come in and retake your blood pressure in a few weeks or measure it every day at home to verify that it's true hypertension and not the result of some other issue affecting you.