5 Common Blood Pressure Mistakes—Where to Get the Most Accurate Reading

Nov 25, 2024 - 11:05 Updated: Nov 24, 2024 - 20:24

5 Common Blood Pressure Mistakes—Where to Get the Most Accurate Reading

Research shows that inaccurate blood pressure readings are rampant, leading to misdiagnosis and mismanagement.

Think your blood pressure reading is accurate? Think again. Small, common mistakes during a routine check may lead to inaccurate readings and misdiagnosis.

Blood pressure readings are a cornerstone of heart health, but research shows they’re often inaccurate. Even a minor error can shift a reading into the hypertensive range, affecting millions of people’s reading and potentially leading to unnecessary treatments and medications. Recognizing common pitfalls—and how to avoid them—can make all the difference.

Accuracy in Question

Most of us trust the quick blood pressure checks at the doctor’s office. But a 2021 study in the American Journal of Preventive Cardiology suggests that trust may be misplaced. Only 1 in 5 cardiologists—excluding preventive cardiologists—follow the recommended guidelines for taking blood pressure despite having confidence in their technique. Preventive cardiologists manage heart disease risk factors before they worsen.

A 2019 position statement from the Lancet Commission on Hypertension Group echoed these concerns, revealing that inaccurate blood pressure readings lead to mismanagement in 20–45 percent of cases in clinical settings. This is often due to outdated techniques or limited training. Even a 5-point error can shift a reading into the hypertensive range, potentially affecting up to 84 million people worldwide.

For Dr. Sean Lucan, a family physician and researcher in preventive medicine, these issues are all too familiar.

“I only remember having my blood pressure checked correctly a single time—at my own PCP’s [primary care provider] office,” he told The Epoch Times. “Maybe people are rushing. Maybe they’re untrained. It’s a huge problem.”

Training gaps contribute to the problem. Blood pressure measurement is usually taught once in medical or nursing school, with little follow-up. Many measurements are also done by medical technicians or support staff, who may receive less formal training than nurses and doctors.

“The problem isn’t limited to clinical staff,” Lucan noted, “it extends to patients using home cuffs without complete, proper education.”

These routine errors can ripple, leading to overdiagnosis and unnecessary medication.

With normal blood pressure at 120/80 mm Hg (millimeters of mercury) and hypertension starting at 130/80 mm Hg, even minor errors can push a reading into the hypertensive range. (The top number is called systolic blood pressure, and the bottom is diastolic pressure.) With 62 million Americans already on medication for high blood pressure, accurate checks are essential to avoid unnecessary treatment and the health risks of overprescribing.

Causes of Inaccurate Blood Pressure Readings

1. Wrong Arm Position

Where you place your arm during a blood pressure check can make a “big difference between a normal reading and a hypertension diagnosis, according to a recent Johns Hopkins study published in JAMA Internal Medicine.

Using electronic blood pressure readings, researchers tested three common arm positions—supported at heart level, resting on the lap, and hanging unsupported—and found significant discrepancies in readings.

The researchers found that when the arm rests on the lap, systolic and diastolic readings can be nearly 4 mm Hg higher than the recommended position of being supported at heart level. An unsupported arm at the side led to even greater increases.

“If you are consistently measuring blood pressure with an unsupported arm, and that gives you an overestimated BP [blood pressure] of 6.5 mmHg, that’s a potential difference between a systolic BP of 123 and 130, or 133 and 140 — which is considered stage 2 hypertension,” study author Sherry Liu said in a press release.

2. Wrong Cuff Size

One of the simplest yet often overlooked factors in blood pressure measurement is cuff size. Like clothing, blood pressure cuffs come in different sizes. For an accurate reading, the cuff must correctly fit the patient’s arm. A cuff that’s too small can overestimate blood pressure, while one that’s too large may underestimate it.

The American Heart Association recommends using a cuff that wraps around at least 80 percent of the upper arm, but studies show incorrect sizes are often used in clinics—particularly for patients with larger or more muscular arms.

A 2023 study published in JAMA Internal Medicine highlights the issue. It found that using a regular-sized cuff on patients needing a larger one led to inflated readings—by nearly 5 mm Hg for a large cuff and as much as 19.5 mm Hg for an extra-large cuff.

These findings reveal the risks of a one-size-fits-all approach when using blood pressure cuffs, especially for people with larger arms. In busy clinical settings, using a standard cuff by default can lead to serious errors. The authors emphasized that proper cuff sizing is crucial to preventing overdiagnosis and unnecessary treatment, recommending “a renewed emphasis on individualized BP cuff selection.”

3. Crossing the Legs

Crossing your legs during a blood pressure check may seem minor, but research shows it can significantly change the reading. A study in the Journal of Hypertension found that when participants crossed one ankle over the knee, their systolic blood pressure rose by an average of 11.4 mm Hg, and diastolic pressure increased by 3.8 mm Hg, compared to readings with feet flat on the floor.

This leg position affects blood pressure because it increases cardiac output—the volume of blood the heart pumps each minute. With more blood flowing, pressure in the arteries rises. However, since peripheral resistance, or the natural resistance in blood vessels, doesn’t adjust to offset this increase, the overall blood pressure spikes. Interestingly, crossing legs at the ankles doesn’t have the same effect on readings.

Study authors recommend that patients keep their feet flat on the floor during measurements to avoid artificially high readings, noting that “the position of legs should be mentioned in all guidelines and publications regarding BP.”

4. Full Bladder

It turns out that needing a bathroom break can do more than just make you uncomfortable—it can also raise your blood pressure. Researchers found that middle-aged women holding a full bladder showed an average increase of 4.2 mm Hg in systolic blood pressure and 2.8 mm Hg in diastolic pressure compared to after they’d relieved themselves.

The effect was most noticeable after three hours, though the increase didn’t continue to rise with longer durations. This suggests that while a full bladder can temporarily boost blood pressure, it’s the discomfort and tension, rather than time, that has the biggest impact.

For anyone who’s waited too long for a restroom, this blood pressure increase is a natural response to bladder distension. A simple trip to the restroom before a blood pressure check can help prevent artificially high readings.

5. White Coat Hypertension

For up to a third of patients, simply visiting the doctor’s office can spike blood pressure readings—a phenomenon known as white coat hypertension. This temporary increase, often caused by anxiety, can elevate systolic readings by as much as 10–20 mm Hg.

Dr. Evan Levine, a cardiologist at Mt. Sinai Health System, manages white coat hypertension by giving patients time to relax and repeating measurements. Studies support this approach, showing that allowing time between readings can reduce anxiety-related spikes. Levine often takes a second reading after the exam, allowing patients to settle down and ensuring more accurate results.

Why Accuracy Matters

Incorrect blood pressure readings are “undoubtedly contributing to patients being over-diagnosed, over-medicated, and subjected to the harms that both bring,” says Lucan.

Inaccurate blood pressure readings can set off a chain reaction of unnecessary treatments and stress. Misdiagnosed hypertension leads some patients to begin lifelong blood pressure medications—such as ACE (angiotensin-converting enzyme) inhibitors or beta-blockers—that carry risks of side effects like dizziness, fatigue, and kidney issues. For those without true hypertension, these side effects are unnecessary burdens.

This problem has caught the attention of national organizations, including the American Heart Association and the American Medical Association, which launched the Target: BP initiative to improve blood pressure management nationwide.

A vital part of this program is re-training health care providers in accurate measurement techniques, ideally every 6–12 months. Studies show that even a 30-minute online module can improve provider skill and confidence. The program also emphasizes out-of-office self-monitoring as a key method for accurate diagnosis.

Lucan advocates for a consistent national approach to blood pressure education. “I really think there should be a unifying educational campaign. Maybe [call it] ‘Check Right,’” he says.

Clear, consistent guidelines would mean fewer misdiagnoses, more effective treatments, and a healthier, more empowered patient community, says Lucan.

There’s No Place Like Home

Experts increasingly recommend that patients monitor blood pressure at home rather than relying solely on clinic readings. Dr. Jackson Wright, director of the Clinical Hypertension Program at University Hospitals, said home blood pressure monitoring (HBPM) has become a preferred method for hypertension management.

Home monitoring became essential during the pandemic as patients turned to remote care. Today, health organizations, including the American Heart Association, widely support it. HBPM provides a day-to-day view of blood pressure trends, offering patients and doctors a more accurate basis for treatment decisions than a single clinic reading.

A 2021 study in the Journal of the American College of Cardiology found that one week of home blood pressure monitoring was more reliable and closely linked to heart health indicators than measurements taken in the clinic.

HBPM also gives patients more control over their health. Studies show that regular home monitoring, especially when combined with telehealth support from nurses, pharmacists, or community health workers, improves blood pressure management and keeps patients more engaged in their care.

As cardiologist Dr. Evan Levine says, “When it comes to BP measurements, there’s no place like home.”

Getting It Right

One high blood pressure reading doesn’t automatically equal hypertension.

Guidelines advise taking at least two readings during a single visit to make sure the result is accurate. Doctors usually repeat the test at a follow-up visit to diagnose hypertension. This two-step process helps rule out temporary spikes caused by stress or simple errors, giving a more reliable picture of a patient’s actual blood pressure.

Manual blood pressure checks were once the gold standard, but most readings today are taken with automatic cuffs. A 2019 meta-analysis found that automated measurements in-office are more accurate than manual readings, closely matching ambulatory monitoring—the best predictor of cardiovascular risk.

For both patients and health care providers, a few straightforward steps can ensure blood pressure readings are as accurate as possible. Lucan recommends emphasizing the fundamentals for reliable measurements, whether in the clinic or at home:

Use the Restroom: Address any bladder or bowel urgency before taking your blood pressure, as this can alleviate temporary high readings.
Avoid Stimulants: Avoid caffeine, nicotine, or exercise for at least 30 minutes prior, as these can temporarily raise blood pressure.
Stay Calm: Take several deep breaths and relax. Don’t talk during the measurement. If you experience white coat hypertension, consider monitoring blood pressure at home.
Positioning: Sit upright with your back supported, feet flat on the floor, and your arm supported at heart level.
Use the Right Cuff Size: Ensure the cuff encircles at least 80 percent of the upper arm for accurate results.
Place the Cuff on Bare Skin: Avoid placing the cuff over clothing to ensure an accurate reading.
Repeat Readings: If the first reading is high, wait a few minutes and take another to ensure accuracy.