Tracking blood pressure at home
Here's why you should regularly monitor your numbers.
- Reviewed by Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
Do you know your blood pressure numbers? The odds are you don't.
Nearly half of U.S. adults have high blood pressure, also known as hypertension, yet estimates suggest only one-third of those with high blood pressure are aware of it. Left untreated, high blood pressure can injure blood vessels, causing them to thicken and stiffen, which can damage the heart, brain, and kidneys.
People are often unaware of their blood pressure because they only have it checked at doctor visits. "So, they don't know if their numbers are high or borderline high, and if so, whether this is a sudden change or something that has been constant for some time," says Dr. Katherine Sakmar, a specialist in hypertension management at Harvard-affiliated Massachusetts General Hospital. "This means that many people don't get the treatment they may need."
A simple way to correct this problem is to check your own blood pressure at home. (See "How to choose a home blood pressure monitor.") Home monitors are inexpensive and easy to use, and they can help identify changes that require medical attention. "Home monitoring also is often more accurate than readings done in doctor's offices, as the stress and nervousness of medical appointments can cause blood pressure to rise," says Dr. Sakmar.
A call to arms
Following certain protocols can help ensure an accurate reading. At least 30 minutes before taking a measurement, avoid consuming caffeine, using tobacco, or exercising. Use the restroom (a full bladder can raise blood pressure), and avoid stimuli like watching TV or conversation. When using your home monitor, follow these steps:
- Use your nondominant arm (your left arm if you are right-handed) unless your doctor suggests using the other arm.
- Support your forearm by resting it on a table with your elbow around heart height.
- Place the monitor's cuff on your bare arm one inch above the bend of your elbow.
- Pull the end of the cuff tight enough that only two fingertips can fit under the cuff's top edge.
- Sit with your feet flat on the floor, and don't cross your ankles, as that can interfere with normal blood flow.
- Push the device's start button, and then remain still during the measurement. The cuff will inflate and then slowly deflate. When the reading is completed, the monitor displays your blood pressure and pulse on the digital panel.
- Wait five minutes and then repeat.
- Average the two readings and record that number.
Dr. Sakmar suggests taking measurements twice daily, morning and evening, for several days to get a baseline reading. (Blood pressure should be lowest when you first wake up and typically rises in the late afternoon and evening.)
After that, depending on your blood pressure goal and doctor's recommendation, you might measure it at least once or twice a week, as well as any time your blood pressure might suddenly change — say, if you feel dizzy or lightheaded or get a sudden headache.
How to choose a home blood pressure monitorYou can buy home blood pressure monitors for $40 to $60 on Amazon or at most drugstores. Look for one with a cuff that automatically inflates. Avoid devices with a wrist cuff or fingertip sensors, as they are not as accurate. The cuff is the right size if the inflatable part completely covers at least 80% of your bare upper arm. Cuffs that are too small can give a false reading. Many models store readings for up to two weeks. Pricier ones can send the data to an app on your smartphone, which makes it easier to keep track of changes and to share the information with your doctor. But you also can easily note your readings with a pencil in a notebook, or take a picture of the reading with your smartphone. Be aware that many home devices are not adequately validated for accuracy, according to a study published online Feb. 15, 2022, by JAMA. Go online to the American Medical Association's ratings site at www.validatebp.org for a list of certified home brands. You also can check your monitor's accuracy by bringing it to your next doctor's visit and comparing its readout with a measurement taken in the doctor's office. An accurate home monitor reading should vary by less than 10%. |
Watching your numbers
Normal blood pressure is now defined as a blood pressure of less than 120 millimeters of mercury (mm Hg) for the systolic reading (the top number) and less than 80 mm Hg for the diastolic reading (the bottom number). Blood pressure is considered high if the systolic number is 130 mm Hg or higher or the diastolic is 80 mm Hg or higher.
Most older adults should aim for blood pressure that is less than 120/80 mm Hg, according to Dr. Sakmar. "But some people may be fine with slightly higher or lower numbers. Your doctor can help you determine your ideal blood pressure range."
In general, you should alert your doctor to any changes outside this range that last longer than a few days, even if you take blood pressure medication. "Monitoring your blood pressure also can reveal if your medication needs adjusting, or if you should take it at particular times during the day," says Dr. Sakmar.
Keep in mind that certain behaviors can affect blood pressure and may alter your readings. Examples include drinking too much alcohol; overusing over-the-counter pain relievers, such as ibuprofen (Advil, Motrin) or naproxen (Aleve); or using decongestants like pseudoephedrine (Sudafed) or oxymetazoline (Afrin). Too much sodium also can cause blood pressure to spike.
Image: © Bill Oxford/Getty Images
About the Author
Matthew Solan, Executive Editor, Harvard Men's Health Watch
About the Reviewer
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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