Pitfalls of Blood Pressure Measurement: Is Your Blood Pressure Really High? A Study Shows the "Arm Position" Can Change the Upper Value by an Average of 6.5

The numbers displayed on the blood pressure monitor are higher than usual. Have you ever felt anxious, wondering, "Did I consume too much salt?" or "Is the medication no longer effective?"

At such times, along with checking your physical condition, it's important to verify the position of your arm during measurement.

Sitting on a chair, wrapping the cuff around your arm, and pressing the button—blood pressure measurement seems simple, but where you place your arm can cause significant differences in the displayed values.

A study from the United States, highlighted by the German news site "op-online" on October 6, 2026, warns about these common measurement habits. Although introduced as new research in the article, the original paper was published online in the medical journal "JAMA Internal Medicine" on October 7, 2024.

Even placing your arm on your knee can result in higher readings

The research team from Johns Hopkins University examined the differences in blood pressure based on arm positioning among 133 adults.

They compared the posture of supporting the arm on a desk, aligning the center of the cuff with heart level, with placing the arm on the knee and letting the arm hang unsupported by the side of the body. The same participants were measured under multiple conditions to assess the impact of posture.

The average differences compared to the standard posture were as follows:

You might think, "If it's on the knee, the arm should be at rest." However, both supporting the arm and aligning the measurement position with heart level are necessary.

The university's explanation also emphasizes the importance of adhering to the basics of properly supporting the arm on a desk or similar surface.

It's not as simple as "subtracting 6.5"

It's important not to misunderstand that the numbers in the table represent the average difference for the group.

Subtracting 6.5 from the blood pressure measured with the arm lowered does not reveal your correct value. What's necessary is to adjust your posture and remeasure.

The study indicates that measurement methods might lead to overestimating hypertension. However, it is not a study that examines the number of participants misdiagnosed or the proportion prescribed unnecessary medication. Also, the same magnitude of difference may not occur with different devices or measurement environments.

From these results alone, one cannot conclude that past hypertension diagnoses were incorrect.

On social media, questions arise about measurement method variations

In the science community on Reddit in October 2024, where this study was introduced, posts reflecting on measurement experiences were observed. The following is a summary of the posts and not a reaction to the 2026 German article.

One user questioned the differences in timing and remeasurement responses among medical institutions. Another user shared an experience of being asked questions by a doctor during measurement. There were also complaints about hurried measurements and accounts of blood pressure being lower at home but higher in the doctor's office.

On the other hand, some posts questioned the clinical significance of a few mmHg differences.

These are individual experiences and opinions and do not represent a survey of the actual conditions across medical institutions. The reasons for the different numbers reported by the posters cannot be explained solely by arm position.

Nevertheless, the questions raised from these reactions are relatable. While we are meticulous about blood pressure numbers, how much do we verify the conditions under which those numbers were obtained?

In Japanese households, first create "the same conditions every time"

If you continue measuring at home, you should align the time and preparation along with the arm position.

The Japan Society of Hypertension's materials for the general public guide using an upper arm blood pressure monitor and measuring in the morning and evening. In the morning, it's within an hour of waking up, before breakfast and medication. In the evening, just before bed is the guideline. After using the restroom, sit on a chair and rest quietly for 1-2 minutes, then measure twice in principle at one time and take the average.

Meanwhile, the American Heart Association advises resting quietly for at least 5 minutes before measurement. While the set rest time varies by material, the common point is to avoid measuring hastily right after moving and to establish calm conditions.

For posture, check the following points:

• Lean back against the chair, do not cross your legs, and keep both feet on the floor.
• Support your arm on a desk or similar surface, and relax your shoulders and arm.
• Align the center of the cuff wrapped around your upper arm with heart level.
• Do not talk or use a smartphone during measurement.

"Heart level" refers to the height of the center of the cuff wrapped around the arm, not the height where the blood pressure monitor itself is placed. If the desk is low, you can adjust by placing a cushion under your arm.

Additionally, the American Heart Association recommends avoiding smoking, caffeine intake, and exercise within 30 minutes before measurement, and using a cuff that fits the arm's size.

To compare daily records, standardize the daily measurement method. To make it easier to continue, decide in advance on the chair and place to rest your arm.

Don't dismiss high values as "just due to posture"

Knowing how to measure is important, but it shouldn't be a convenient excuse to ignore high numbers.

According to materials from the Japan Society of Hypertension, a systolic blood pressure of 135mmHg or higher or a diastolic blood pressure of 85mmHg or higher measured at home is a guideline for hypertension. Do not self-diagnose based on a single number; continue measuring and show the records to your doctor.

There is "white coat hypertension," where blood pressure is high in the doctor's office but low at home, and "masked hypertension," where it is normal in the office but high at home. Home measurements can provide clues to conditions not apparent from office readings alone.

Even for those undergoing treatment, do not reduce or stop medication on your own if a lower value is obtained after remeasurement. It's important to report changes in measurement posture along with records to your primary care physician.

To make the numbers on the blood pressure monitor more useful health information, before pressing the button next time, ensure your arm is well-supported and the cuff is at heart level.

Source URL

1. op-online: Article dated October 6, 2026.
   https://www.op-online.de/welt/blutdruck-korrekt-messen-wie-eine-falsche-armposition-die-ergebnisse-beeinflusst-zr-94526829.html

2. JAMA Internal Medicine: Original research paper comparing measurement differences based on arm position in 133 adults. Published on October 7, 2024. Used for verifying research methods, figures, and limitations.
   https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2824754JAMA Network

3. Johns Hopkins University School of Medicine: Official announcement explaining the research results and the importance of properly supporting the arm during measurement.
   https://www.hopkinsmedicine.org/news/newsroom/news-releases/2024/10/johns-hopkins-medicine-study-finds-commonly-used-arm-positions-can-substantially-overestimate-blood-pressure-readingsJohns Hopkins Medicine

4. Japan Society of Hypertension "Let's Measure Blood Pressure at Home": General materials showing measurement times, rest periods, measurement frequency, and home blood pressure guidelines.
   https://www.jpnsh.jp/data/selfmonitoring.pdfjpnsh.jp

5. American Heart Association: Guidance on preparing for home blood pressure measurement, arm and cuff positioning, recording, and not stopping medication on your own.
   https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings/monitoring-your-blood-pressure-at-homeAmerican Heart Association

6. American Heart Association: Explanation of correct measurement posture at home, including back, feet, and arm support.
   https://www.heart.org/en/news/2022/05/23/monitoring-blood-pressure-at-home-can-be-tricky-heres-how-to-do-it-rightheart.org

7. Reddit・r/science: Public comments on the research introduction in October 2024. Used for summarizing social media reactions. Posts are personal experiences and opinions, not used as medical evidence.
   https://www.reddit.com/r/science/comments/1fyapbu/blood_pressure_may_read_falsely_high_if_the_arm/