Harvard Heart Letter | September 2008 (updated January 2012)
Home monitoring makes sense if you have high blood pressure.
Your blood pressure changes from hour to hour, sometimes even minute to minute. Standing up from a chair, watching an exciting show on television, eating a meal, listening to soothing music, being stressed — even the time of day — influence your blood pressure. It jumps around so much that you are more likely to get a "normal" reading if you check it at home rather than in the doctor's office.
That idea underlies a recommendation from the American Heart Association (AHA), American Society of Hypertension, and Preventive Cardiovascular Nurses Association (Hypertension, July 2008). They urge individuals with high blood pressure, or at high risk for developing it, to become blood pressure do-it-yourselfers. There are many good reasons to follow their advice:
Find your real blood pressure. The measurement your doctor or nurse takes is just a just single frame from an ongoing movie. In some individuals, that snapshot tells the whole story, and is an excellent approximation of their usual blood pressure. In others, it isn't. Up to 20% of people diagnosed with high blood pressure have white-coat hypertension. This is a temporary spike in blood pressure brought on by the stress of trekking to and seeing a doctor. Still others have what's called masked hypertension — normal blood pressure in the doctor's office but high blood pressure everywhere else.
Improve your control. People who check their blood pressure at home tend to be more successful at keeping it under control. Timely feedback helps. Instead of a getting a blood-pressure reading once every few months under unusual conditions (in a doctor's office), you can get a reading every week or so at home. Taking the measurements yourself also helps. People who actively participate in their care generally do better than those who take a hands-off, let-the-doctor-do-it approach.
Track your progress. You can't feel your blood pressure get better — or worse. Measuring it at home offers vital information about whether your lifestyle changes and the medications you are taking are having their desired effects.
Save time and medications. Monitoring your blood pressure at home may mean fewer trips to the doctor's office. If you have white-coat hypertension, it may also mean taking fewer, or no, blood pressure medicines.
Run with the right crowd. Of every 100 people with high blood pressure, 70 or more don't have it under control. Checking your pressure at home and acting on the results can help you join the "in" crowd who do. A study shows that people who checked their blood pressure at home and e-mailed the results to a pharmacist who offered advice were far more likely to keep their blood pressure in check than those who merely measured it at home or those who had it taken by a doctor every now and then (Journal of the American Medical Association, June 25, 2008).
Who needs to do this?
The new recommendation says home monitoring should be done by most people "with known or suspected hypertension." That includes the whopping 73 million Americans with high blood pressure. It also includes the millions more with type 2 diabetes or chronic kidney disease, who are at high risk for developing high blood pressure. Women who become pregnant should consider checking their blood pressure at home, since high blood pressure is a common, and problematic, side effect of pregnancy. You might also think about it if you are seriously overweight, if you smoke, or if high blood pressure runs in your family.
Picking the right machine
There are dozens of different home blood pressure monitors on the market. For best accuracy and ease of use, buy one with a cuff for the upper arm that automatically inflates and that automatically records the pressure. Models that store readings for a week or two can simplify record keeping. The AHA doesn't recommend wrist or finger home blood pressure monitors.
Consumer Reports occasionally reviews home blood pressure monitors. Its last such review was in September 2011. The ReliOn HEM-741CREL got a "best buy" rating.
Taking your blood pressure at home
To get the most accurate blood pressure reading, support your arm at heart level, wrap the cuff around your bare upper arm, and follow the directions on your machine.
Do it right
When it comes to measuring blood pressure, technique matters. Doing it wrong can give you a reading that's too high or too low. (Click here to see a brief video on using a home blood pressure monitor.)
There are two things to do before you start. First, check your machine against the one in your doctor's office. Second, make sure you have the right size cuff — the inflatable part should encircle at least 80% of your upper arm.
When you first start to check your blood pressure at home, measure it early in the morning, before you have taken your blood pressure pills, and again in the evening, every day for a week. After that, follow the plan your doctor recommends, or check it one or two days a month. Each time you take a reading:
Avoid caffeinated or alcoholic beverages, and don't smoke, during the 30 minutes before the test.
Sit quietly for five minutes with your back supported and feet on the floor.
When making the measurement, support your arm so your elbow is at the level of your heart.
Push your sleeves out of the way and wrap the cuff over bare skin. Measure your blood pressure according to the machine's instructions. Leave the deflated cuff in place, wait a minute, then take a second reading. If the readings are close, average them. If not, repeat again and average the three readings.
Don't panic if a reading is high. Relax for a few minutes and try again.
Keep a record of your blood pressure readings and the time of day they are made.
Checking blood pressure at home won't cure hypertension, but it will help control the most common cause of stroke and a big contributor to heart attack, heart failure, and premature death.