24 hour blood pressure monitor

High blood pressure does not usually cause symptoms, but it raises the risk of stroke and heart disease, so it needs measuring accurately. A single reading in a surgery can be misleading, especially if you feel anxious there, the so-called white coat effect.

For that reason NICE, which advises the NHS, recommends a 24 hour (ambulatory) blood pressure recording to confirm high blood pressure when a clinic reading is between 140/90 and 180/120. It is also used to see how well blood pressure treatment is working across a whole day and night. High blood pressure is one of the main cardiac risk factors.

A cuff goes around your upper arm, connected to a small recorder. You wear it home and hand it back the next day. It inflates by itself, usually every 30 minutes during the day and less often at night, and squeezes your arm for a few seconds, which can feel uncomfortable until the air releases.

Carry on with your normal day. When the cuff starts to inflate, keep still and quiet with your arm relaxed and straight, sitting down if it is safe to. You cannot bath, shower or swim while wearing the monitor.

The readings taken while you are awake are averaged, using at least 14 of them. If that daytime average is 135/85 or more, it confirms high blood pressure. NICE sets this threshold 5 points below the clinic one of 140/90.

Patients are strongly encouraged to buy their own blood pressure machine and take regular readings at home. Take two readings a minute apart, morning and evening, and write them down. When home readings are used to confirm high blood pressure, NICE suggests doing this for at least 4 days, and ideally 7. At home, 135/85 or more is considered high. Our article on managing blood pressure naturally covers what you can do day to day.