Do you have hypertension? If not, you are almost an anomaly. 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. No wonder 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.
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.
One 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 recent 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.
Common Mistakes When Measuring Blood Pressure:
Please scroll to the photo at the top of the page. Can you identify some obvious mistakes?
- The patient is sitting on the exam table without back support
- The patient is sitting on the exam table without having her feet touching the floor
- The patient has her arm hanging down! It should be supported at heart level.
- The cuff looks a bit too small for her arm
- 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:
- 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.
- 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!
- 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.
- 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.
- 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!
- Did you get to go to the bathroom prior to a BP measurement? A full bladder can impact your readings.
- 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:
- 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.