See separate leaflet called ‘High Blood Pressure (Hypertension)’ for more general information. This leaflet is just about ways of recording you blood pressure.
Why is it important for you to monitor your blood pressure?
Some people find it a bit stressful to have their blood pressure checked in a doctor’s surgery. This is known as white coat syndrome. If your blood pressure is raised, the doctor will not know if this is because of the stress of being in the surgery (white coat high blood pressure) or because your blood pressure is usually and persistently high, even when relaxed at home. It is a persistently high blood pressure that is known as hypertension.
The National Institute for Health and Clinical Excellence (NICE) recommends that if your blood pressure is found to be 140/90 mm Hg (= millimetres of mercury) or above, you should check it at home and during your normal day-to-day activities. The best way to do this is using an ambulatory blood pressure monitor which can be worn for 24 hours a day. But, if you find this uncomfortable or inconvenient, a home blood pressure monitor can be used.
Ambulatory blood pressure monitoring is also sometimes used to check how well medicine used to treat hypertension is working.
Ambulatory blood pressure monitoring
The ambulatory blood pressure monitor consists of a cuff which wraps round your arm. The cuff is attached to a small electric recording device on a belt or strap worn on your body. The doctor or nurse who supply the device should make sure the cuff is the right size for your arm. You should keep the device safe and dry and not have a bath or shower whilst wearing it. From time to time you will feel a tightening sensation in your arm whilst the cuff is inflating but this will not last very long and most people will not be worried by it. Try not to move your arm whilst the cuff is inflating. If the device cannot record your blood pressure it will try to repeat the process up to three times. The machine is usually set to record twice an hour whilst you are awake and hourly at night.
The ambulatory monitor can be worn whilst going about your everyday activities. So, it will give an accurate impression about how your blood pressure behaves under normal circumstances. The doctor will look at at least 14 readings spread throughout the day to decide whether or not you have hypertension.
Home blood pressure monitoring
This is an alternative to ambulatory blood pressure monitoring. The process for doing this will be exactly the same as that used by the doctor or nurse in the surgery. You will be given a blood pressure monitor to use at home. Wrap the cuff around your arm just above the level of the elbow. (Check the instructions with the monitor to make sure the tubing is in the right position.) You should be seated comfortably with your arm supported (for example, on a table) at the level of your heart. Press the button to inflate the machine and make a note of the reading.
You should measure your blood pressure twice a day, once in the morning and once in the evening. On each occasion you should take two readings, one minute apart. You should take readings for at least four days, and ideally for seven days. The doctor should use all the readings, apart from those taken on the first day, to calculate your average blood pressure.
What your readings mean
- If your blood pressure is below 140/85 mm Hg at the surgery, it will be considered normal.
- If your blood pressure is above 140/85mm Hg at the surgery but your average ambulatory or home reading is below 135/85 mm Hg, it will be considered normal.
- If your blood pressure at the surgery is 140/90 mm Hg or above and your average ambulatory or home reading is above 135/85 mm Hg, it will be considered high.
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