Before you begin to monitor your blood pressure at home, it's important to know that differences between left-arm and right-arm (interarm) blood pressure are common. Several studies have been done to determine what is a ‘normal’ variation between right and left arm. In general, any difference of 10 mm Hg or less is considered normal and not a cause for concern.
Since some studies showed that the average interarm systolic blood pressure difference was significantly greater in patients with known coronary artery disease, it’s a good idea to discuss differences higher than 10 mm Hg with your doctor.
When you have your blood pressure taken at the doctor’s office for the first time, it’s recommended that it be taken in both arms. But if you’re measuring your blood pressure at home, readings are often more easily taken in the non-dominant arm. If your home blood pressure readings are different from those taken in the doctor’s office, be sure to discuss this with your healthcare professional.
Many factors affect blood pressure. The fact that there are differences in right and left arm readings emphasizes the importance of measuring blood pressure in both arms initially to prevent the misdiagnosis of high blood pressure. If one arm consistently has higher blood pressure than the other, that arm should be used to measure your blood pressure.
- Make sure the cuff fits.
Measure around your upper arm and choose a monitor that comes with the correct size cuff.
- Be still.
Don't smoke, drink caffeinated beverages or exercise within the 30 minutes before measuring your blood pressure.
- Sit correctly.
Sit with your back straight and supported (on a dining chair, for example, rather than a sofa). Your feet should be flat on the floor; don't cross your legs. Your arm should be supported on a flat surface (such as a table) with the upper arm at heart level. Make sure the middle of the cuff is placed directly above the eye of the elbow. Check your monitor's instructions for an illustration or have your healthcare provider show you how.
- Take multiple readings.
Each time you measure, take two or three readings one minute apart and record all the results.
- Measure at the same time daily.
It's important to take the readings at the same time each day, such as morning and evening, or as your healthcare professional recommends.
- Accurately record all your results.
Record all of your readings, including the date and time taken. Share your blood pressure records with your healthcare team. Some monitors have built-in memory to store your readings; if yours does, take it with you to your appointments. Some monitors may also allow you to upload your readings to a secure Web site after you register your profile.
- Understand the readings.
Optimal blood pressure is less than 120/80 mm Hg (systolic pressure is 120 AND diastolic pressure is less than 80). Read Understanding Blood Pressure Readings to learn more about what the numbers mean.
- Consult your healthcare professional if you get several high readings.
A single high reading of blood pressure is not an immediate cause for alarm. However, if you get a high reading, take your blood pressure several more times and consult your healthcare professional to make sure you (or your monitor) don't have a problem. When blood pressure reaches a systolic (top number) of 180 or higher OR diastolic (bottom number) of 110 or higher, emergency medical treatment is required for hypertensive crisis.
- Watch our Home Blood Pressure Monitoring Video:
- Print the How to Measure Your Blood Pressure sheet as a helpful reminder.
Heart360 allows you to track your blood pressure and the steps you're taking to manage it online. You can print your readings to take or fax to your doctor. This online tool also works on Microsoft's Health Vault personal health record storage system, which allows you to share your data with your doctor electronically. Or, if you prefer to record your BP readings on paper, download and print our Blood Pressure Tracker.
This content was last reviewed on 08/04/2014.