Inaccurate blood pressure measurement could lead to incorrect diagnosis and inappropriate treatment. The chance to reduce the risk of heart attack or stroke could also be missed. Over 3000 blood pressure monitors are available but less than 15% of these have been properly tested for accuracy.
Check for accuracy
“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.
Acute meal ingestion, caffeine or nicotine use can all affect BP readings, leading to errors in measurement accuracy. If the patient has a full bladder, that can lead to an error in systolic BP of up to 33 mm Hg, and the white-coat effect can have an error of up to 26 mm Hg.
Blood Pressure Cuff Placement
If the cuff is too small, it can add 2 to 10 points to your bp measurement. Be sure to roll up your sleeve for a blood pressure test and also let your doctor know if the cuff feels too tight around your arm.
Home blood pressure monitoring is not a substitute for medical visits. Home blood pressure monitors might not always be correct. Even if you get readings that are typical for you, don't stop or change your medications or your diet without talking to your care provider first.
You could have white coat hypertension. This condition occurs when blood pressure readings at a health care provider's office are higher than they are in other settings, such as at home. It's called white coat hypertension because people who measure blood pressure sometimes wear white coats.
Measure your blood pressure twice daily. The first measurement should be in the morning before eating or taking any medications, and the second in the evening. Each time you measure, take two or three readings to make sure your results are accurate.
Don't check your blood pressure too often.
Some people find that they become worried or stressed about small changes in their readings if they take them too often. Worrying can also raise your blood pressure in the short term, making your reading higher than it should be.
Blood pressure has a daily pattern. Usually, blood pressure starts to rise a few hours before a person wakes up. It continues to rise during the day, peaking in midday. Blood pressure typically drops in the late afternoon and evening.
Blood pressure changes throughout the day. Your blood pressure is typically at its lowest right after waking up. It tends to vary by up to 30% across the day. This is because of hormone changes, activity level, and eating.
The resulting anxiety can elevate blood pressure 10 points or more.” Studies have shown that clinics rarely take two or more blood pressure readings, even though the ACC/AHA guidelines suggest that doing so could reduce the effects of WCH.
Everyone's blood pressure rises and falls many times during the course of a single day, sometimes even within minutes. Many factors contribute to these changes, including physical activity, emotion, body position, diet (especially salt and alcohol intake), and sleep deprivation.
Don't eat or drink anything 30 minutes before you take your blood pressure. Empty your bladder before your reading. Sit in a comfortable chair with your back supported for at least 5 minutes before your reading. Put both feet flat on the ground and keep your legs uncrossed.
The simplest way to measure your own blood pressure is to purchase an automated cuff. Automatic blood pressure machines are easy to use, and they're helpful if you have any hearing impairments. These types of blood pressure cuffs have a digital monitor that will display your blood pressure reading on a screen.
The current American Heart Association/American College of Cardiology Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults recommends five minutes of rest before a blood pressure test.
Something as simple as keeping yourself hydrated by drinking six to eight glasses of water every day improves blood pressure. Water makes up 73% of the human heart,¹ so no other liquid is better at controlling blood pressure.
The most common error when using indirect blood pressure measuring equipment is using an incorrectly sized cuff. A BP cuff that is too large will give falsely low readings, while an overly small cuff will provide readings that are falsely high.
While both numbers in a blood pressure reading are essential for diagnosing and treating high blood pressure, doctors primarily focus on the top number, also known as systolic pressure.
Taking your blood pressure at home can help doctors see the trend. “But I caution patients not to take it every five minutes, which can happen if they are concerned about high readings. That becomes a bad cycle. Do it intermittently—once or twice a week,” she said.
Take Second (and Maybe Third) BP Readings in Routine Follow-Up for Hypertension. In a third of patients with elevated blood pressures on initial readings, second readings were lower than 140/90 mm Hg.
Check it twice
It's ideal to measure your blood pressure twice a day for two weeks leading up to a doctor's appointment, or following a change in medication. At each sitting, measure your blood pressure three times, but discard the first reading as it tends to be inaccurate.
It's normal for blood pressure to vary somewhat throughout the day. Stress, exercise, and sleep can all make a difference. But if your blood pressure often changes significantly from one healthcare visit to another, there may a problem.
Manual blood pressure measurements may not be as accurate as the automatic devices that take multiple measurements. If your doctor still uses a manual device to check your blood pressure, you risk being misdiagnosed, experts say.