"There are a lot of monitors out there, and some of them aren't very good," Goff said, warning that even upper-arm monitors could be inaccurate. "Patients should take their device to their doctor or nurse to make sure it agrees pretty well with the device being used in the office."
Dr. John D. Bisognano, a cardiologist at the University of Rochester Medical Center, agrees that wrist monitors can be problematic. "If the patient uses the monitors with great precision and reproducibility, they work okay," he said by e-mail. "But if not, the readings can vary widely and cause unnecessary alarm to the patient and provide inaccurate data. They may have some limited use in overweight patients who cannot obtain accurate readings using arm monitors, even with a large cuff."
Still, some patients are able to get good numbers from wrist monitors. A few of McDermott's patients are able to use them, although many others are not.
If your doctor recommends a home monitor, you can get one at the drugstore or online for about $75. You don't need a prescription.
Once you've got the proper kind of monitor, you need to use it correctly. It's tempting to take your blood pressure throughout the day, just to see how you're doing. Or, maybe your life is busy and you check your blood pressure when you remember. Neither of these methods gives you numbers your doctor can really use.
Eating, smoking, exercising and drinking coffee can all affect your numbers. To get the best readings, the heart association recommends checking first thing in the morning and again just before bed.
And they say to take more than one measurement each time, at least at first. To help your doctor diagnose high blood pressure — or make sure you don't have it — the recommendation is to check at least twice in the morning and twice before bed, every day for a week.
For patients, one of the most important things about home blood pressure monitoring may be that it puts you in control.
"There are examples of other chronic conditions where people are very involved in their own care," Wake Forest's Goff said.
And different kinds of home monitoring help people keep their illness under control.
"People with diabetes sometimes have to check their blood sugar four times a day," he said. "People with chronic heart failure have to weigh themselves daily. High blood pressure is another one of those conditions" for which patients could be more involved in their own care.
If you're monitoring your blood pressure at home, you can see the effects of a new medication, of improving your diet, of getting more exercise, or of cutting back on alcohol.
Family physician McDermott sees another potential advantage, too, just to having home monitors out there. "A good thing about it, and I've seen this happen too: hypertension is silent. And if you can measure your blood pressure, or a friend's blood pressure, and you can catch it, you can save a life."