How accurate are home blood pressure monitors?

"Home blood pressure monitors may be inaccurate in 5% to 15% of patients, depending on the threshold for accuracy used," according to Dr. Swapnil Hiremath, a kidney specialist at Ottawa Hospital in Canada.

How do I know if my blood pressure monitor is accurate?

“If the systolic blood pressure (the top number) on your cuff is within 10 points of the monitor, then it's generally accurate,” he says. Most home blood pressure machines last for about two or three years. After that, check it at your doctor's office annually to make sure it's still accurate.

Things you have to know when buying home blood pressure monitor

1. Size matters

The size of the cuff is the most important feature to check when you’re selecting a blood pressure monitor. The size relates to the circumference of your upper arm. A cuff that doesn’t fit properly on your arm may give you inaccurate readings. The 2017 High Blood Pressure Clinical Practice Guidelines, which both the American College of Cardiology and the American Heart Association endorse, recommends these sizes:

• Adult small: Arm circumference of 22 to 26 centimeters (about 8.5 to 10 inches).
• Adult average: Arm circumference of 27 to 34 centimeters (about 10.5 to 13 inches).
• Adult large: Arm circumference of 35 to 44 centimeters (about 13.5 to 17 inches).

2. Choose arm cuffs over wrist cuffs

You can purchase a blood pressure monitor at any drugstore or online. No matter where you buy yours, getting a monitor with an automatic cuff that wraps around your upper arm. It’s called a brachial blood pressure monitor.

3. Don’t overpay

Forget the bells and whistles. They boost the cost of the monitor and are often unnecessary. Sure, Bluetooth connectivity and storing your readings in the cloud are cool features, but you don’t really need them.

4. Avoid smart apps

If you look at any app store, you’re likely to find dozens of blood pressure measurement apps for your smartphone. Certain apps claim to measure your blood pressure through pulse wave velocity, which essentially looks at the wave form in the artery of your finger. “But those are often inaccurate,” he adds. The last thing you want is to obtain false information and be falsely scared — or falsely reassured — about your blood pressure numbers.”

5. Check for accuracy

Most monitors you find in a drugstore or online are fine,  If the systolic blood pressure (the top number) on your cuff is within 10 points of the monitor, then it’s generally accurate. Most home blood pressure machines last for about two or three years. After that, check it at your doctor’s office annually to make sure it’s still accurate.

6. Take three

There’s one extra feature you might consider to help boost a monitor’s accuracy: taking three measurements automatically. Some monitors do this each time you check your blood pressure. They take a first reading; wait 30 to 60 seconds and take a second reading; then wait 30 to 60 more seconds, and take a final measurement.