How is blood pressure measured?

Blood pressure is usually measured with a device that goes around the upper arm. This is called a “blood pressure cuff.” This is often done in a doctor’s office. But some people also check their blood pressure themselves, at home or at work.

Blood pressure is explained with 2 numbers. For instance, your blood pressure might be “140 over 90”:

• The first (top) number is the pressure inside your arteries when your heart is contracting.
• The second (bottom) number is the pressure inside your arteries when your heart is relaxed.

The table shows how doctors and nurses define high and normal blood pressure.

If your blood pressure gets too high, it puts you at risk for heart attack, stroke, and kidney disease. High blood pressure does not usually cause symptoms. But it can be serious.

Sometimes, your blood pressure can get too low. This is called “hypotension.” If your blood pressure is too low, you might have symptoms like feeling weak, dizzy, or lightheaded.

Why do I need my blood pressure measured?

Your doctor or nurse might want to check your blood pressure:

• As part of a routine check-up – Your doctor or nurse will record your blood pressure and see if it changes over time.
• To check if you have high blood pressure
• To check how well your medicines are working (if you take blood pressure medicines)

In some cases, your doctor might take a few different blood pressure measurements over a short period of time (for example, over 1 week).

How do I prepare for blood pressure measurement?

Your doctor or nurse will tell you if you need to do anything special to prepare.

To make sure that your measurement is as accurate as possible:

• Avoid caffeine for at least 30 minutes before your appointment. Caffeine is found in some drinks, like coffee and soda.
• Tell your doctor if you are taking any medicines. Certain medicines can affect your blood pressure.
• Tell your doctor or nurse if you smoke. Avoid smoking for at least 30 minutes before your appointment.
• Go to the bathroom and empty your bladder before the measurement.
• Avoid running, jumping, or walking for 5 minutes before your measurement.
• Stay still while your blood pressure is being measured. Try not to talk or move too much.
• Wear a short-sleeve shirt, if you can, or a shirt made of thin fabric.

What happens during blood pressure measurement?

When it is time for your blood pressure measurement, your doctor or nurse will:

• Ask you to sit in a chair with your back supported and your legs uncrossed. They might ask you to rest your arm on a table.
• Wrap a blood pressure cuff around your upper arm. The cuff will fit snugly around your arm.
• Hold a stethoscope on the inside of your elbow to listen to your pulse (heartbeat).
• Squeeze a rubber bulb connected to the cuff – This will force air into the cuff. It will feel tight on your arm.
• Take your blood pressure measurement – They will listen to your pulse and read a dial on the cuff to get the measurement.
• Let the air out of the cuff, and take the cuff off of your arm.

In some cases, your blood pressure measurement is read by a machine that is connected to the arm cuff.

Once your measurement has been taken, your doctor or nurse will tell you what it is. Ask them if you have questions about what the numbers mean.

What happens after blood pressure measurement?

Your doctor or nurse will review your blood pressure measurement and talk to you about what it means.

If your blood pressure is too high or too low, your doctor will talk to you about what might be causing it and what you can do to get it into the normal range. In some cases, they might want you to have more tests or come in for another appointment. This can help them figure out why your blood pressure is too high or too low.