Check your blood pressure at home

Content provided by the Faculty of the Harvard Medical School

Check your blood pressure at home

For a more accurate measure of your blood pressure, and help keeping it under control, try keeping tabs on it at home.

Are you interested in halving your chances of having a heart attack or stroke? You don’t need a new drug to stop inflammation or stabilize vulnerable plaque. You needn’t find a clinical trial of stem cells to heal injured blood vessels or heart muscle. The secret is safer, cheaper, and far more mundane: Routinely check your blood pressure and work to lower it if it is high.

Neither part of this prescription for prevention is as simple as it sounds. Controlling high blood pressure (hypertension) takes some work. It involves paying attention to what you eat, exercising (or exercising more), making other lifestyle changes, and taking medications if needed. Merely finding out if you have high blood pressure or tracking the results of your efforts to keep it under control can also be difficult. Why? Because doctors are notoriously bad at measuring blood pressure.

So do it yourself.

Why bother with blood pressure?

A healthy blood pressure is 120/80 or below. The chance of having a heart attack or stroke doubles with each increase of 20/10. So if your blood pressure is 135/85 — a level that many doctors consider normal — you have almost twice the risk as someone with a healthy blood pressure.

Blood pressure tends to rise with age. Only 10% or so of 30-year-olds have high blood pressure, compared with more than 75% of 75-year-olds.

Home show

The most popular devices for home use are digital monitors. They are easy to use, especially for people who are hard of hearing, since they don’t require a stethoscope. There are four main types of these: automatic and manual arm monitors, wrist monitors, and finger monitors. Home monitors are available in pharmacies and electronics stores, via the Internet, and elsewhere. They range in price from under $30 to $150 or more.

Automatic arm monitors use a cuff that wraps around your upper arm. Once in place, it inflates automatically, records your blood pressure, and deflates by itself. The results show up on a screen and are usually easy to read. A manual or semiautomatic monitor works much the same way, except you inflate the cuff by squeezing a rubber bulb. Some automatic models accurately measure blood pressure in people with an irregular heartbeat; others don’t.

A wrist monitor slips over your wrist like a watch. It works automatically and displays the results on a watchlike screen. These aren’t as accurate as arm monitors, sometimes because people forget to hold their wrist at heart level when checking their blood pressure. They can be a good alternative for people who have trouble wrapping a cuff around the upper arm.

Finger monitors slide over the tip of a finger. Although they are extremely easy to use, they tend to be the least accurate type of home blood pressure monitor.

With so many options available, how can you choose a reliable model? Consumer Reports tested 16 digital monitors for its June 2003 issue. The magazine’s testers concluded that automatic arm monitors were the best choice for most people. The British Hypertension Society also tests home monitors and lists those meeting its standards on its Web site, www.bhsoc.org.

Reasons to do it yourself

Knowing your blood pressure is too important to leave to your doctor. Even the American Heart Association recommends home monitoring — as a supplement to doctors’ office recordings — in its 2005 guidelines on blood pressure measurement.

Checking your blood pressure at home makes sense for several reasons. It gives you and your doctor a more accurate idea of your blood pressure. It can help fine-tune the strategy for keeping your blood pressure in check. And it just might make you more invested in controlling a silent problem that has no symptoms until it spawns a heart attack or stroke or leads to heart or kidney failure.

Home monitoring is also useful for people whose blood pressure is different in the doctor’s office than it is at home. Some people have white-coat hypertension — a jump in blood pressure in the doctor’s office. Others have masked hypertension — normal blood pressure in the doctor’s office but high pressure at home.

Ask your doctor to help you set a schedule for checking your blood pressure. At first, check it at different times of the day. Good “baseline” times are in the morning just after waking up, before breakfast, and before your evening meal. You may need to check more often if your medicine is being adjusted or if you are having problems with low or high blood pressure.

If your blood pressure is high, or it’s headed that way, a home monitor is a solid investment. And remember, a single monitor can serve the whole household.

Measuring your blood pressure

When it comes to measuring blood pressure, technique is just as important as the quality of your equipment. Here are some tips for getting the most accurate readings from your home monitor.

Before you get started, make sure the cuff is the right size for you. The inflatable part should be placed over bare skin and should encircle at least 80% of your upper arm. If it is too small, you’ll need to buy a larger cuff.

To make sure your machine is accurate, bring it to your doctor’s office. Ask your doctor or a nurse to check your pressure with the office equipment before or after you do it with your home monitor.

The first few times you measure your blood pressure at home, do it on both arms or wrists. If the reading is higher on one side than the other — this isn’t unusual — use the arm or wrist with the higher reading all of the time. The next time you see your doctor, tell him or her about the side-to-side difference.

Each time you measure your blood pressure:

Avoid caffeinated beverages, alcohol, and tobacco for at least 30 minutes before the test.
Sit quietly for five minutes with your feet on the floor and your back supported. The quiet part is important — talking can raise your blood pressure by 20 points.
Make sure your arm is supported and that the monitor is at heart level; this is particularly important if you use a wrist monitor.
If you are using an arm monitor, push sleeves out of the way and wrap the cuff over bare skin.
Take two or more readings, and average them.
Keep a record of your blood pressure readings and the time of day they are made. This is especially important if you are taking blood pressure medications, which may not work all day long.

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Last updated:	August 21, 2006

Medical content reviewed by the Faculty of the Harvard Medical School. Harvard Health Publications, Copyright © 2007 by President and Fellows of Harvard College. All rights reserved. Used with permission of StayWell.

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