Ask the Pharmacist: Your guide to measuring blood pressure

How is blood pressure measured?

Blood pressure is usually measured with two numbers.

1. Systolic pressure (top number) is the pressure of blood in the vessels when the heart pumps or squeezes.

2. Diastolic pressure (bottom number) is the pressure of blood in the vessels while the heart relaxes between heartbeats.

According to guidelines from the National Heart, Lung, and Blood Institute (NHLBI), the optimal blood pressure is 120/80 mmHg. Hypertension is diagnosed when the systolic pressure is 140 mmHg or higher or the diastolic pressure is 90 mmHg or higher. If you have kidney disease, diabetes or heart failure, your doctor may want your blood pressure goal to be lower. Your doctor will help you find your blood pressure goal.

Why is it important to correctly measure blood pressure?

It is very important to get an accurate blood pressure reading. A change of as little as 5 to 10 mmHg on the systolic or diastolic pressures can mean the difference between a normal and a high reading. As a result, an incorrect reading may cause you to either start treating your normal blood pressure when treatment is not needed, or you may fail to treat high blood pressure that needs to be controlled.

Rules for correct blood pressure measurement

1. Rest quietly in a chair for at least five minutes before the reading. It takes several minutes for your blood pressure to return to normal after activity such as walking to your doctor’s office or climbing stairs.

2. Don’t drink anything containing caffeine and don’t smoke for at least 30 minutes before a blood pressure measurement. Caffeine and nicotine are stimulants that can temporarily increase your blood pressure.

3. Make sure that you are seated upright with your legs uncrossed and both feet placed flat on the floor in front of you.

4. Your arm should be supported on a table at a height that is level with your heart. Your arm should be bare and your palm should face upward.

5. The cuff around your upper arm should fit snugly, not too tight and not too loose. No more than two fingers should fit under the edge of the cuff.

6. Sit quietly while your blood pressure is being measured so the person taking the reading can hear the sounds needed to obtain an accurate measurement.

7. At least two blood pressure measurements should be taken.

These rules should be followed whether your blood pressure is being monitored in your home or in your doctor’s office. Don’t be afraid to speak up and ask questions.

Record blood pressure measurements regularly

If you are measuring your blood pressure at home or some place away from the doctor’s office, don’t forget to record your measurements and take them with you to your next doctor’s visit. Your doctor’s office can then compare their measurements to yours. If your home measurements are unusually high (e.g. greater than 140/90 mmHg), you should consider scheduling a special visit with your doctor’s office to have them re-check your blood pressure.

What is Hypertension?

High blood pressure (hypertension) is a condition you need to manage the rest of your life. Living with uncontrolled high blood pressure can greatly increase your risk for other serious health problems such as stroke, heart attack, or heart failure. There are several keys to properly control blood pressure:

• accurate blood pressure measurement;

• healthy diet;

• exercise;

• proper use of medications;

• regular visits to your doctor.