By measuring your blood pressure at regular intervals over 24 hours, your doctor is able to get a clearer picture of how your blood pressure changes throughout the day. There are a number of reasons why your doctor might suggest this test:

• They may want to find out if your high blood pressure readings in the clinic are much higher than they are away from the clinic (called the “white coat effect”). 
• They may want to see how well your medicines are working, to make sure they are controlling your blood pressure through the day.
• They may want to see if your blood pressure stays high at night. If this is the case, they may need to change or adjust your medicines.

Because the test is being carried out to find out what your normal daily blood pressure is, it is important to carry on with your normal routine and do all the things you would normally do. The only things you should avoid doing for the day are swimming and having a bath or shower.

At the end of the 24 hours you can remove the machine and cuff and bring it back to the office when instructed. The machine will have stored all your readings and these will then be analyzed.

To allow the machine to work properly, it is important to make sure that the tube to the machine is not twisted or bent. Also, just before the machine is about to take a reading, it will beep. When this happens you should:

• sit down, if possible
• keep the cuff at the same level as your heart 
• keep your arm steady

You will also be asked to keep a diary of what you were doing just before the reading was taken, what time you went bed and got up, and if and when you took your medications. Some people find 24-hour ABPM distracting and uncomfortable: if you feel like this when the readings are being taken, be sure and inform your doctor when you return the device as it may affect your reading.