En español | According to research presented last fall at the American Heart Association's annual meeting, more than 70 percent of the 103 million American adults who have hypertension could get it under control by doing one simple thing: monitoring it at home.
"It's important to do this, especially if you've already been diagnosed with high blood pressure, or if your doctor is trying to figure out whether you have it,” says internist Michael Hochman, director of the Gehr Family Center for Health Systems Science at Keck Medicine of USC in Los Angeles. “This way you can make sure that you're on the right medications, at the appropriate doses, or, on the flip side, that you're not taking medications unnecessarily.”
Strapping on that arm cuff monitor at home can also give a more accurate picture of your blood pressure than occasional office visits alone. At a doctor's office, some will experience “white coat hypertension,” where their blood pressure shoots up in a way it doesn't when they take a reading from home. And about 12 percent of American adults will experience the reverse, called masked hypertension, which means getting normal readings at a physician's office but higher ones at home.
Because of these variations as well as a number of other reasons, experts say that people whose blood pressure is creeping up into the range of 130/80 mm Hg or higher should make sure they're monitoring themselves at home. Here are five things you should know about how to do so correctly:
Buy a good model
Home blood pressure monitors come in arm cuff, wrist cuff and finger models. Of the three, an automatic upper-arm cuff-style model is the way to go, advises Luke Laffin, a cardiologist at Cleveland Clinic. (Wrist and finger models produce less reliable readings.) Make sure the cuff fits: If it's too large or small, you could get the wrong reading.
Make sure it's accurate
Before using a monitor for the first time, have your doctor's office check it against their model, says Laffin. A 2016 study found that about a third of home blood pressure monitors were off by at least five points. “We usually check a patient's blood pressure with our machine, then about two minutes later check it on their monitor,” he says. “If their systolic [upper number] reading is within about 10 mm, it's accurate enough to use.” Also a good idea: Have a doctor or nurse observe you taking your own blood pressure reading, to make sure you're doing it correctly.
You shouldn't smoke, consume caffeine or exercise within 30 minutes of checking your blood pressure. If you have to urinate, do so before taking a reading. Measuring blood pressure with a full bladder can add 10-15 points to your reading, according to the American Heart Association.
How you sit also matters. Slouching or sitting with your back or feet unsupported can raise your reading by five to 10 points, and crossed legs can increase your reading by anywhere from two to eight points.
For the best results, sit in a chair with your back supported, feet flat, and legs uncrossed. Your arm should be supported on a flat surface (such as a table) with the upper arm at heart level. Don't multitask during the reading, either. Talking to your partner or chatting on the phone while taking your blood pressure can add 10-15 points to your number. Stay silent and still. Finally, put the cuff on bare skin — strapping it on top of clothing, rather than a bare arm, can add 10-40 mm Hg to a measurement.
If you're monitoring your blood pressure at home, make sure you take it at the same time daily. There's also no need to take it more frequently than once a day. “I have many patients who are overzealous and take their blood pressure three to four times a day, which drives them nuts because it's impossible to make sure that you've been doing all the things you're supposed to do — like resting for five minutes and cutting out caffeine for 30 minutes — that many times a day,” says Anuradha Lala-Trindade, a cardiologist at the Icahn School of Medicine at Mount Sinai in New York City. In the morning, before you've eaten or had your morning coffee, is an ideal time to take a reading.
Take multiple readings
The American Heart Association recommends taking two or three readings one minute apart. You can record the results, either by using a printable format (PDF) or tracking it online. This will allow you to keep a record that you can bring to your appointments. Some monitors also allow you to upload your readings to a secure website. If any one reading seems off, don't throw it away. Keep it with the rest and talk to your doctor about it at your next appointment. If your blood pressure readings suddenly exceed 180/120 mm Hg, wait five minutes and test again. If the next reading is still unusually high, contact your doctor immediately.
This story was updated with new video content on October 22, 2019.