What is 24-hour blood pressure monitoring?

High blood pressure (hypertension) often has no symptoms, so many people do not know they have it. But over time, it can increase your risk of serious health problems.

Roughly 3 in 10 adults in the UK have high blood pressure, and it is linked to around half of all heart attacks and strokes.

That's why it's important to know your own blood pressure because you can seek help from your doctor if you see it's getting higher.

However, a normal blood pressure can vary depending on where you have it checked. It might be higher at a clinic when you feel stressed, compared to when you check it at home when you might be more relaxed.

Often, 1 or 2 high readings do not give your doctor enough information to diagnose high blood pressure. So they may arrange 24-hour blood pressure monitoring, also known as ambulatory blood pressure monitoring, to make a clear diagnosis and tailor treatment for you.

• Learn more about high blood pressure readings.

How does 24-hour blood pressure monitoring work?

The way 24-hour blood pressure monitoring works is that it takes regular blood pressure readings as you go about your usual daily activities and while you're asleep.

You'll wear a cuff around your upper arm that is attached to a small blood pressure monitor worn around your waist or shoulder.

It’s programmed to take regular blood pressure readings over the 24 hours, usually every 20 to 30 minutes during the day and every hour overnight.

The cuff will inflate and then deflate every time a reading is taken.

For an accurate reading, keep your arm still and relaxed by your side or rest it straight out on a table when the cuff starts to inflate.

Try to go about your usual daily activities, including exercise, as much as possible during the 24-hour monitoring period, to give an accurate picture of your blood pressure levels.

As well as diagnosing high blood pressure, your doctor may recommend this test to find out:

• how well your blood pressure medicines are working throughout the day
• whether your blood pressure stays high at night, which may mean your treatment needs to be reviewed or adjusted. 

What to avoid when using the monitor

There are few things to keep in mind when wearing the monitor to make sure it works as intended.

You’ll need to avoid:

• moving your arm when the cuff starts to inflate
• getting the monitor and cuff wet
• swimming, showering or having a bath
• driving.

What does fitting the monitoring device involve?

A nurse or cardiac physiologist can fit a 24-hour blood pressure monitor at a hospital or your GP practice.

They will place a blood pressure cuff around your upper arm. This is usually your non-dominant arm, for example, your left arm if you're right-handed. 

You may notice the attached monitor looks like a normal blood pressure monitor you can buy at larger pharmacies or online from the BHF shop.

It’s programmed to take regular blood pressure readings over the 24 hours, usually every 20-30 minutes during the day and every hour overnight.

The cuff will inflate and then deflate every time a reading is taken.

For an accurate reading, keep your arm still and relaxed by your side or rest it straight out on a table when the cuff starts to inflate.

Try to go about your usual daily activities, including exercise, as much as possible during the 24-hour monitoring period, to give an accurate picture of your blood pressure levels.

If your GP has prescribed any medicine, keep taking it before your appointment unless you are told otherwise.

You can also ask if a friend or family member can come into the appointment with you, if you would find this helpful.

You may be asked to remove your top when having the monitor fitted or move any clothing covering your arm. So, you may want to wear something that's easy to take off or a short-sleeved shirt.

How do you sleep with a monitor?

At night, it might be easier to unclip the monitor from around your waist and place it under your pillow or on the bed while you sleep.

Try to lay on your back or your uncuffed side so the tubing does not get pinched and blood can flow freely to the cuffed arm.

Unfortunately, the cuff may disturb your sleep when it inflates, but remember it’s important to wear the monitor overnight so your doctor can see what happens to your blood pressure while you sleep.

What happens when 24 hours is up?

Once the 24-hours is over and your monitor has stopped taking readings, you can give it back to the hospital or clinic.

They will examine all the recorded readings and calculate an overall average blood pressure reading.

Depending on the reason for the monitoring and the results, your doctor may diagnose high blood pressure, change or add a new medication to help manage your blood pressure and talk about lifestyle changes which may benefit you.

Doing more physical activity, cutting down on salt, keeping to a healthy weight and stopping smoking can all help with managing your blood pressure. 

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