What happens during the test?
The doctor uses a device called a sphygmomanometer (a pressure gauge attached to a blood pressure cuff) to measure your blood pressure. The blood pressure cuff is placed around your upper arm just above the elbow and a stethoscope is held over your brachial artery, the blood vessel just on the inside of your elbow joint. The cuff is inflated to temporarily block blood from flowing through the artery.
As the air is let out of the cuff, your doctor is waiting to hear the onset of a whooshing noise and when it stops. The onset of the noise indicates that the pressure in your arteries is equal to the pressure in the cuff, allowing blood to flow again. This pressure is the systolic pressure, and this will be indicated on the gauge. This is the first number (e.g., 120 if your blood pressure is 120 over 80) and roughly indicates how strong the heart pushes blood through the arteries.
When the whooshing noise disappears, this is the diastolic blood pressure, which roughly indicates the residual pressure in the arteries. Blood pressure is read with the systolic blood pressure over the diastolic blood pressure. For example, a blood pressure of "120/80 mmHg" (measured in millimeters of mercury) is referred to as "120 over 80."
Your doctor may also use an electronic or digital device to measure your blood pressure. These devices need to be compared to the technique above to make sure they are working correctly.
How should I prepare for this test?
Wear a short-sleeved shirt when you have your blood pressure monitored and avoid drinking beverages with caffeine or smoking for 30 minutes before the test. You should also sit down with your back supported and feet flat on the floor for at least five minutes before the test. You should also go to the bathroom before the test. Most importantly, relax.
Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any medication allergies and medical conditions that you may have. Ask your doctor or pharmacist whether you need to stop taking any of your medications before the test.
What can I expect after the test?
You can return to your normal activities immediately after the test. However, call your doctor if you begin to experience worsening heart-related symptoms following the test.
Results
Ask your doctor for your blood pressure reading as well as help in understanding what it means. For many people, a healthy blood pressure reading is less than 120/80 mmHg.
Blood pressure is usually considered high when it is greater than 140/90 mmHg consistently. If you are being treated for high blood pressure, your blood pressure should be below this target. However, some people with kidney disease or diabetes need to aim for even lower blood pressure targets.
There is a new category called pre-hypertension. People have pre-hypertension if the systolic blood pressure (the first number) is between 120 mmHg and 139 mmHg, and diastolic blood pressure (the second number) is between 80 mmHg and 89 mmHg. Pre-hypertension is considered a warning to people that they could develop hypertension and that diet changes and exercise should be started. Medications do not need to be started when a person has pre-hypertension.
If you are concerned about your blood pressure, you can monitor your blood pressure at home. Ask your doctor if monitoring your blood pressure at home is right for you.