Seven Mistakes to Avoid When Measuring Blood Pressure!

We are exhausted! We have been exhorting health professionals for years to carefully follow guidelines when measuring blood pressure. Despite our ongoing efforts, many visitors to this website tell us that their BP continues to be measured incorrectly. Does it matter? A new study published in JAMA Internal Medicine (Oct. 7, 2024) states unequivocally that it absolutely matters! When the arm is not supported, as in the photo at the top of this page, systolic blood pressure is overestimated by 6.5 points and diastolic BP is overestimated by 4.4 points. More alarming, “…among higher-risk groups: SBP [systolic blood pressure] was overestimated by approximately 9 mm Hg.”

The authors from the Johns Hopkins study concluded:

“This crossover randomized clinical trial showed that commonly used arm positions (lap or side) resulted in substantial overestimation of BP readings and may lead to misdiagnosis and overestimation of hypertension.”

In this study the authors specifically wanted to know how arm position changes blood pressure readings. The scientists recruited 133 middle-aged participants and assigned them to one of three conditions. The arm was supported on a desk, or the hand was supported in the lap or the arm was hanging unsupported by the side.

Each volunteer also had a separate measurement taken with the arm supported on a desk, providing a “gold-standard” measurement. Both lap and side arm positions resulted in higher measurements of both systolic and diastolic blood pressure.

The authors concluded:

“This crossover randomized clinical trial shows that not adhering to the guideline-recommended arm position and support during BP measurement can result in overestimation of BP by 4 to 10 mm Hg. This degree of BP error could lead to a substantial number of people being overdiagnosed with hypertension.”

Do You Really Have Hypertension?

The AHA (American Heart Association) estimates that 122 million Americans have high blood pressure (Circulation, Feb. 23, 2023). This puts nearly half the adult population at risk for heart attacks, heart failure, strokes and kidney disease, among other health problems.

It’s hardly any wonder that the first thing most physicians require at an office visit is a blood pressure reading. But measuring blood pressure is a lot harder than most people realize! This seemingly simple procedure is actually fraught with potential mistakes. You might be surprised to learn how often an error in technique results in a faulty reading. This can lead to either under- or over-treatment of hypertension.

Why Arm Position Matters!

Here is how the authors of the latest study in JAMA Internal Medicine introduce their research:

“Hypertension is the leading cause of cardiovascular disease and preventable mortality worldwide. Accurate blood pressure (BP) measurement is a cornerstone of hypertension diagnosis and management. The latest clinical practice guidelines emphasize several key steps for accurate measurement, including appropriate cuff size selection, back support, feet flat on the floor with legs uncrossed, and appropriate arm position (ie, midcuff positioned at heart level with arm supported on a desk or table). Despite these recommendations, proper arm position is commonly overlooked in daily practice. For example, in the US, BP is often measured with patients seated on an examination table without any arm support or with inadequate support (eg, resting on their lap or supported by health care professionals holding the patient’s arm).”

Please take a moment to look at the photo at the top of this page one more time. The patient is “seated on an examination table without any arm support…”

Readers Report a Startling Number of Mistakes:

We suspect that many blood pressure readings are taken incorrectly. That’s in the doctor’s office, clinic and hospital. Judging from our own experience and reports from readers, we think that few health professionals are familiar with the guidelines set up by the American Heart Association (AHA). We have observed technicians in a highly rated hospital make mistake after mistake when measuring blood pressure.

Mary is a retired RN and recently shared her experience:

“I am taken straight back from waiting room to the exam room and told to sit on the exam table with my feet swinging in the breeze. The assistant takes my blood pressure with my arm outstretched with no support. She asks me questions throughout the procedure.

“The blood pressure cuff may, or may not be, the correct size for my arm. My bladder often needs to be emptied. I may have just eaten. Because of the ‘fast in/fast out’ in physician offices, there is rarely an opportunity to sit still for 5-10 minutes prior to a BP reading.

“Take your own blood pressure readings at home on a regular basis and keep a record.”

Another reader describes faulty technique:

“My blood pressure is taken incorrectly by medical assistants and nurses at least 40 percent of the time. The result is readings that are too high. When I ask them to take it again, it is always lower.

“They use an extra-large cuff on everyone, but they never wait, and they often don’t have my arm at heart level. My home readings are always quite a lot lower.”

Another reader reports that the wrong cuff size can hurt like heck:

“I need a larger cuff, and I do better with manual blood pressure readings. When the medical assistant slaps my arm into a standard cuff on an automated machine, it hurts a lot and makes my fingers numb. I want to howl. Often, if I ask for a larger cuff, they say they don’t have one. Frequently, they also don’t have a manual sphygmomanometer or someone who knows how to use it correctly.”

Why Does Measuring Blood Pressure Matter?

Another reader also mentions the cuff size. She says:

“I weigh 95 pounds so my arm at the bicep measures about 9 inches. Usually the nurse takes my blood pressure over my clothes instead of putting it on my skin. Often the large cuff is almost doubled over on itself. I’ve always thought the cuff needs to be against the skin.”

Are these readers getting excited about trivia, or does cuff size make an important difference? A study shows that it matters quite a bit (JAMA Internal Medicine, Aug. 7, 2023).

The investigators concluded:

“In this randomized crossover trial, miscuffing resulted in strikingly inaccurate BP measurements.”

To be specific, when the cuff was too large, as for our 95-pound reader, the readout was significantly lower than the actual pressure. If, on the other hand, someone with a large arm is measured with an ordinary sized cuff, the measurement comes out much higher than it should.

In this study, the average blood pressure reading for such individuals was 144/88 when measured with a regular-size cuff, but when the appropriate large-size cuff was used, the average reading was 125/79. That could easily lead to an unnecessary prescription for blood pressure pills.

How Would You Know If the BP Cuff is the Right Size for Your Arm?

We recently wrote about a study in the journal Hypertension (Sept. 25, 2024) that determined most blood pressure devices for home use come with an arm cuff that is too small for many people. You can read the “FULL FREE TEXT” by clicking in the upper right corner.

Delores shared this experience about cuff size and technique when measuring blood pressure:

“At the doctor’s office my blood pressure is taken over the sleeve of my shirt, my arm is not at the right position, they use a bariatric cuff even though my arm is not big, and sometimes they talk to me, and I know I get “white coat” syndrome. If I sit for a while quietly, my blood pressure will drop significantly, sometimes between 20-30 points. When I question some of the procedures they tell me it doesn’t matter.

“If they listen to me, they get a significantly different measurement. It depends on who is doing the measurement. If they measure it a second time they get a lower figure. I do measure my blood pressure at home and it is always lower.”

You will find a guide to blood pressure cuff sizes at the bottom of this article. The next time someone measures your blood pressure at a clinic or doctor’s office you can tell them what size cuff to use.

Common Mistakes When Measuring Blood Pressure:

Please scroll to the photo at the top of the page one more time. Can you identify some obvious mistakes?

1. The patient is sitting on the exam table without back support
2. The patient is sitting on the exam table without having her feet touching the floor
3. The patient has her arm hanging down! It should be supported at heart level.
4. The cuff looks a bit too small for her arm
5. The stethoscope is tucked under the cuff without firm support by the health professional

Spanked By a CMA!

A certified medical assistant (CMA) took us to task for specifically mentioning “technicians” when it comes to measuring blood pressure. We got spanked pretty hard!

Q. You criticized certified medical assistants for inaccurate blood pressure recordings. It is offensive to single us out.

All medical personnel, including doctors, are guilty of hurrying through this measurement and not positioning the patient properly. Using an outdated or uncalibrated sphygmomanometer is not the CMA’s fault.

Patients would be wise to purchase their own home blood pressure devices or go to their pharmacies for weekly or monthly readings. Most doctors respect a person who can produce a written record of readings. This might make a difference in their treatment protocol.

A. We apologize for criticizing CMAs for improper blood pressure measurement technique. As you have correctly pointed out, many other health care professionals may fail to follow the appropriate procedures (see photo above for example).

We have described in detail all the correct steps for proper BP monitoring in our eGuide to Blood Pressure Solutions. They include time to relax, a bathroom break, proper positioning, correct cuff size, no talking, multiple measurements and home verification with an accurate device.

There are many personal blood pressure monitors available ranging from about $25 to $150. We list our favorite in the guide.

This reader also points out a couple of common errors.

Three Bad Mistakes to Avoid When Measuring Blood Pressure:

Q. The instructions for my home blood pressure machine make it clear that you should be sitting for five minutes at least, with your arm at just below heart height.

In the doctor’s office, you hop off the scale, climb on a stool and seat yourself with your legs dangling. Then the nurse takes your BP with your arm hanging down, nowhere near the level of your heart. How can that be accurate?

A. We too have been shocked to observe how often blood pressure measurements in the clinic are performed incorrectly. We do not understand why the people who are charged with measuring blood pressure are not instructed in the AHA recommendations:

Checklist Prior to Measuring Blood Pressure:

1. Did you get time to relax? Whether you take your BP yourself at home or have it measured in a clinic setting, always take 5 to 10 minutes to sit and relax prior to any reading.
2. Did you sit in a comfortable chair with back support and an arm rest? Were your feet flat on the floor? Never allow any health professional to take your blood pressure while you sit on an exam table with your feet dangling and no back rest or arm support!
3. Did someone measure your arm circumference to make sure the BP cuff is the right size? We have NEVER seen a technician do this. If your arm is smaller or larger than average, the wrong sized cuff will lead to misleading BP readings.
4. Was your arm supported at heart level while someone was measuring blood pressure? This is critical to an accurate reading. We are constantly dismayed to see people having their blood pressure read with their arm dangling at their side.
5. Did the technician, nurse or doctor talk to you or ask you a question while measuring blood pressure? If you responded, the chances are very good that your blood pressure was falsely elevated. NEVER speak during the minute or two it takes to pump up the cuff and let the air all the way out!
6. Did you get to go to the bathroom prior to a BP measurement? A full bladder can impact your readings.
7. Did the doctor, nurse or technician take your BP at least twice during your visit? One single reading is not adequate. It is recommended that two measurements be made some time apart. The two readings can then be averaged to get a better sense of your true blood pressure.

Measuring Blood Pressure At Home:

We have been advocating for home blood pressure measurement for more than 40 years. Because of all the mistakes that can be made in the clinic, we think regular home readings may be more reliable. They also lead to better blood pressure control (Lancet, March 10, 2018).

When purchasing a blood pressure monitor, please make sure the cuff size is correct:

Mid-arm circumference:

• Less than 26 cm (1o.2 inches) = Small Adult Size Cuff
• 26-34 cm (10.2 to 13.4 inches) = Regular AdultSize Cuff
• 34-44 cm (13.4 to 17.3 inches) = Large Adult Size Cuff
• More than 44 cm (17.3 inches) = Extra Large Adult Size Cuff

For more information on the proper technique for measurement as well as nondrug strategies for controlling BP, we offer this link:

You may also find our eGuide to Blood Pressure Solutions helpful. In addition to tips about proper technique for measuring blood pressure, we recommend affordable devices that have scored highly in objective head-to-head testing. There are also strategies for getting blood pressure under control. You will find this eGuide in the Health eGuides section of this website. Share your own story about blood pressure measurement in the doctor’s office or clinic in the comment section below.