Beverly told us about a recent appointment where a health care worker knelt on the floor in front of her and wrapped the cuff around her arm while it dangled toward the ground.

Not surprisingly, the reading was sky-high.

“When she looked up and asked if I had taken my blood pressure medicine that morning,” Beverly wrote, “I could barely keep a straight face.”

Daniel described something just as common—an assistant first took his blood pressure with his arm in his lap (result: very high) and then repeated the measurement correctly with his arm on a table (result: excellent):

“He obviously knew the right way to do it,” Daniel said. “So why didn’t he do it the first time?”

A comment about bad blood pressure readings came from Renee, a registered nurse with more than two decades of experience:

“I am so tired of correcting experienced nurses in how to take blood pressures correctly—even cardiac nurses! I get resistance every time. And no one taught this properly when I was in nursing school.”

If cardiac nurses struggle with proper blood pressure technique, what are the chances the rest of us are getting accurate numbers during routine office visits?

The Silent Culprit: Arm Position

A large 2024 study published in JAMA Internal Medicine (Oct. 7, 2024) highlighted one of the biggest and most consistent problems in everyday practice: arm position.

The researchers discovered that two of the most common positions used in clinics—the arm resting in a lap or hanging at the side—regularly inflate blood pressure numbers.

Here are the authors conclusions about bad blood pressure readings in their own words:

“This crossover randomized clinical trial demonstrates the considerable effect of arm position on BP readings. 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…BP readings in either position were sufficiently high to raise concerns for overdiagnosis and overtreatment. These findings were consistent, and also more extreme, among higher-risk groups: SBP [systolic blood pressure] was overestimated by approximately 9 mm Hg among individuals with hypertensive BP when their arm was positioned at the side.”

Think back to your last appointment:

• Were your feet flat on the floor?

• Was your back supported?

• Was your arm resting on a table at heart height?

• Were you sitting quietly for several minutes beforehand?

If not, the reading may not have reflected your true blood pressure.

Another Common Cause of Bad Blood Pressure Readings:

After arm position I would rank cuff size as a major mistake when it comes to measuring blood pressure. Here is a little quiz for you:

• Have you ever had your arm measured before a nurse or technician measured your blood pressure?
• Has anyone ever selected BP cuff to match your arm size?

How would you know if your arm is too small or too big to fit a “standard” blood pressure cuff?

We turn to the American Family Physician for guidance. An article by Kenny Lin, MD, MPH was posted on August 21, 2023. The title:

For Accurate Blood Pressure Measurement, Cuff Size Matters:

Here is the overview:

“Four adult BP cuff sizes are available in the United States: small (20 to 25 cm mid-arm circumference), regular (25.1 to 32 cm), large (32.1 to 40 cm), and extra-large (40.1 to 55 cm). Although most primary care offices have cuffs in multiple sizes, home BP monitors sold in pharmacies typically use the regular cuff size, which is too small for many adults.”

I am going to make this a bit easier for those who do not think in metric sizes:

• 20 cm → 7.87 in

• 25 cm → 9.84 in

• 25.1 cm → 9.88 in

• 32 cm → 12.60 in

• 32.1 cm → 12.64 in

• 40 cm → 15.75 in

• 40.1 cm → 15.79 in

• 55 cm → 21.65 in

I am going to try to make this even easier:

1. If the circumference of your arm is between 7.87 in. to 9.84 in. you need a small cuff
2. If the circumference of your arm is between 9.88 in. to 12.6 in. you need a regular cuff
3. If the circumference of your arm is between 12.64 in. to 15.75 in. you need a large cuff
4. If the circumference of your arm is between 15.79 in. to 21.65 in. you need an extra-large cuff

Now you are equipped to ask the medical technician if he or she would be kind enough to measure your arm size the next time you get your blood pressure measured at a clinic. Of course if your arm is “standard size” you don’t need to go through this exercise. But, if your arm circumference is small or large, you definitely need the right size cuff!

Here is what Dr. Lin reports in his article for American Family Physician:

Why Are There So Many Bad Blood Pressure Readings?

Diane shared this revealing observation from her gynecologist’s office:

“The nurse just wanted a number for her laptop. When I mentioned that I needed to sit quietly and keep my arm at heart level, she told me her method was more accurate. They often take my BP on a sleeved arm unless I’m wearing short sleeves.”

Another reader told us that a rushed technician used the wrong cuff, placed it over a sweater, inflated it painfully, chatted through the process, and took only one reading. When the physician repeated the measurement at the end of the visit—done correctly this time—their blood pressure dropped nearly 40 points.

These aren’t isolated mistakes. This is a widespread problem.

The 22 Most Common Blood Pressure Reading Mistakes

A massive review of 224 studies identified 22 ways blood pressure readings can go wrong (Physiological Measurement, Sept. 5, 2022). Among the most frequent:

• Cuff too small or too large

• Arm unsupported or at the wrong height

• Sitting on an exam table with feet dangling

• Measuring over clothing

• Talking during the reading

• Taking a single measurement instead of multiple readings

• Not resting beforehand

• Cold exam rooms

• Drinking coffee, tea, or alcohol within 30 minutes

• A full bladder

• Anxiety (white coat hypertension)

Each of these can shift the reading enough to change a diagnosis.

White Coat Hypertension: Jeanni’s Smart Strategy

Jeanni deals with what researchers call “white coat syndrome.” At home her numbers are fine, but in a medical office they jump.

Her solution to avoid bad blood pressure readings:

“Before an appointment, I take my pressure for three days, write the readings down, and show them to the nurse or doctor.”

This is exactly what hypertension experts recommend.

Why Home Blood Pressure Monitoring Matters

Home monitoring isn’t just convenient. It’s increasingly considered the gold standard by hypertension specialists for diagnosing and managing high blood pressure.

Why?

• It avoids the “white coat” stress many people experience in a medical office.

• It produces multiple readings over time, not a single rushed measurement.

• It reflects your real life — not your “doctor’s office blood pressure.”

But only if you do it correctly.

Home monitoring is an excellent idea—but only when done correctly. A study in BMC Primary Care (Jan. 23, 2023) found that most people measure incorrectly unless they’ve been trained.

How to Get Accurate Blood Pressure Numbers at Home

Here’s the right method:

1. Prepare

• Empty your bladder.

• Sit quietly for 5–10 minutes.

• Avoid caffeine and alcohol for 30 minutes.

2. Position yourself properly

• Sit in a chair with back support.

• Feet flat on the floor.

• Arm supported at heart level.

• Correct cuff size.

• Cuff on bare skin.

3. Measure correctly

• Don’t talk.

• Take at least two readings, a few minutes apart.

• Average the results.

• Bring your device to the doctor to confirm its accuracy.

What to Do at Your Next Appointment To Prevent Bad Blood Pressure Reading:

You are your own best advocate.

If your arm is hanging, your feet are dangling, the cuff is too small, or the technician starts chatting during the reading, say something. Politely, but firmly.

Try:

“Could we make sure my arm is at heart height? That gives the most accurate reading.”

or

“Could we take a minute for me to sit quietly first?”

Most professionals appreciate patients who care about accuracy—especially when you explain that the wrong numbers can lead to the wrong treatment.

The Bottom Line

Blood pressure measurement should be simple, but the reality is that technique determines accuracy. Even small mistakes can produce dramatically different numbers.

Understanding how blood pressure readings go wrong—and what to do about it—gives you the power to protect your health and avoid unnecessary medications or missed diagnoses.

Taking blood pressure readings correctly at home can go a long way towards providing your healthcare providers accurate information. That will help create a strategy for excellent blood pressure control.

For more guidance about blood pressure monitoring, the DASH diet, home remedies, and evidence-based strategies for managing hypertension, visit us at PeoplesPharmacy.com and read our eGuide to Blood Pressure Solutions. It can be found under the Health eGuides tab. 

If you know someone who has high blood pressure and/or measures their blood pressure at home, please send them this post. It will help them avoid bad blood pressure readings. You can do that easily by scrolling to the top of the page and clicking on the icons for email and/or social media. Thank you for supporting our work.