Faulty Blood Pressure Readings Are Shockingly Common

Blood pressure measurement used to be challenging. It required a doctor or nurse to use a device containing a glass tube with a lot of mercury. An inflatable cuff was attached to the arm of the patient and to the sphygmomanometer. The cuff would be pumped up to cut off blood flow. The mercury in the glass column would climb to 160 or 18o and gradually come down as air was let out of the cuff. Meanwhile, the healthcare professional would listen attentively with a stethoscope to hear sounds of blood coming back through the artery in the arm. There was a lot of room for error. Nowadays we have digital devices that are much easier to use and highly accurate. But mistakes when taking blood pressure readings are disappointingly common, both at the doctor’s office and at home.

How Many Americans Have High Blood Pressure?

According to the CDC, 120 million Americans have high blood pressure. That’s nearly half of all adults and is based on old recommendations of

“…systolic blood pressure greater than 130 mm Hg [millimeters of mercury] or a diastolic blood pressure greater than 80 mm Hg…”

The American Heart Association/American College of Cardiology (AHA/ACC) now recommend that everyone should lower their blood pressure below 120/80. I suspect the number of people categorized with some degree of hypertension would be even higher than 120 million given the new goal.

There Are Way Too Many Mistakes with Blood Pressure Readings!

Blood pressure readings are supposed to be simple and objective–just numbers on a screen. But if blood pressure is measured incorrectly–at a clinic or at home–the results can lead to under- or over-treatment.

One reader shared this example of blood pressure readings done wrong:

Q. You have written about blood pressure measurement, so I thought I’d share my experience. I recently went to my doctor and, as usual, my blood pressure was taken incorrectly.

The tech used my right arm hanging down at my side, asking questions the whole time. In addition, the cuff was on my arm within 30 seconds of entering the exam room and the cuff was blown up too hard. I told her she should use my left arm and support it at the level of my heart. She was obviously miffed and said it didn’t matter.

When my doctor came in, she assured me we’d check it again. That check, at the end of the visit, was done correctly. The result was a nearly 40-point drop in systolic and about 15 points in diastolic readings. Technique makes a huge difference. If my doctor had considered only the tech’s measurement, she might well have prescribed a blood pressure pill I don’t need.

A. A review of 224 studies identified 22 common errors that can affect blood pressure accuracy (Physiological Measurement, Sept. 5, 2022).

Here are just a few of the errors these investigators uncovered during blood pressure measurement at home or in the clinic:

• Clothing
• Arm position
• Body posture
• Back support
• Interval between measurements
• Cuff size
• Room temperature
• Stimulant drinks (coffee)
• Talking

The authors make it a point to encourage patients to avoid:

“…stimulating drinks (coffee, alcohol, etc) exercise and smoking for 30 minutes before the formal measurement. In addition to this, they need to ensure that the bladder has been emptied.”

Health Professionals Also Mess Up Blood Pressure Readings:

A study published in JAMA Internal Medicine (Oct. 7, 2024) noted:

“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).”

Here is a photograph of what they are talking about. This represents horrific technique and could easily lead to misleading blood pressure readings:

Doctor measuring blood pressure of overweight woman in hospital or clinic

The authors go on to state:

“Specifically, when BP measurements are obtained with arm positions frequently used in clinical practice (ie, on the lap or at the side), the readings obtained are markedly higher than those obtained with the arm positioned according to published guidelines.”

How to Avoid Common Home Blood Pressure Mistakes:

A Polish study published in BMC Primary Care (Jan. 23, 2023) revealed a lot of mistakes when people take their own blood pressure readings at home. The investigators filmed these patients in the act, so to speak.

They concluded:

“Significant differences were observed in the mean BP readings recorded by patients and investigators; SBP [systolic blood pressure] and DBP [diastolic blood pressure] readings were higher when measured by patients.”

Improving Blood Pressure Readings at Home:

• Sit quietly at least 5 to 10 minutes before you turn on the BP monitor
• Measure your arm circumference and make sure you have the proper BP cuff size!
• Always position your arm and the blood pressure cuff at heart level–not dangling or resting in your lap
• Place the BP cuff over bare skin rather than over a shirt or sweater
• Sit upright with your back supported and your feet flat on the floor
• Do not drink coffee, tea or any alcoholic beverages 30 minutes before taking your blood pressure readings
• Always empty your bladder before measuring your blood pressure
• Take multiple readings. Wait several minutes between readings and then average them.
• Never talk when you are taking a blood pressure reading!
• Take your BP monitor to the doctor’s office and ask the person who monitors blood pressure to test it against the office equipment
• Ask your healthcare professional to instruct you on the proper technique for managing blood pressure readings

Here’s a little quiz:

Please scroll to the top of this article and look at the photograph of the man taking his own blood pressure. Can you count the 4 ways he is taking his home blood pressure incorrectly? Answer at the bottom of this page.

If you would like more information about blood pressure monitoring and ways to better control hypertension you may wish to consult our eGuide to Blood Pressure Solutions. It provides detailed information on the proper technique for BP measurement, including the dimensions for proper cuff size. Always make sure the cuff that your doctor’s office uses is correct! This online resource can be found under the Health eGuides tab.

Bottom Line:

Blood pressure matters, but accurate measurements are critical because they drive medical decisions about treatment. If mistakes are made, unnecessary medicines may be prescribed. The reverse is also true. A correct diagnosis of hypertension may be missed and someone may go untreated, raising the risk for a heart attack or stroke.

Because blood pressure readings are often inaccurate at home as well as in the clinic, people need to be proactive. Not allowed to empty your bladder and sit quietly prior to BP measurement? Speak up. If the cuff is too small or too big, speak up. The same if you are not seated in a chair with a back and your arm is not supported at heart level: speak up. If the technician does not take multiple readings with time in between each reading, speak up. When anything does not seem right, SPEAK UP!

Please share this article with friends and family members. We suspect that 1 out of every 2 of your acquaintances has blood pressure that is greater than 120/80. They may find this article of interest. Thank you for supporting our work. You can learn more about good blood pressure measuring technique, the DASH diet, dark chocolate, beet juice and hibiscus tea at this link.

Answers to the quiz:

1. The man in the photograph does not have both feet flat on the floor.
2. His arm is not supported at heart level.
3. He is drinking ice water.
4. The cuff size looks to be too small for his muscular arms

We hope that the next time you have your blood pressure measured it is done correctly, whether at home or at the clinic.