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How is blood pressure measured?

Blood pressure is measured in “millimetres of mercury” (written as “mmHg”) using a simple machine. When you have it measured, it will be written as two numbers, a top number and a bottom number. For example, if your reading is 120/80mmHg, your blood pressure is 120 over 80.  The top number is the systolic pressure, and the bottom number is the diastolic pressure.

As a general guide:

  • 140/90mmHg or over – you may have high blood pressure

Most doctors use 140/90mmHg as the cut-off point for diagnosing high blood pressure (hypertension). This is the point where your risk of serious health problems goes up. They might prescribe medications and advise you to make changes to your lifestyle to bring your blood pressure down.

  • 120/80mmHg up to 140/90mmHg – pre-high blood pressure

Also called high-normal blood pressure. This is not high blood pressure, but it is a little higher than it should be and means you could go on to develop high blood pressure. See how you can make healthy changes to your lifestyle to lower it.

  • 90/60mmHg up to 120/80mmHg – ideal blood pressure

This is the normal range for a blood pressure reading. At this level, you have a much lower risk of heart disease and stroke. Following a healthy lifestyle will help you to keep it in the healthy range.

  • 90/60mmHg or lower – you may have low blood pressure

Low blood pressure doesn’t always cause symptoms, but can sometimes make you feel faint or dizzy or could be a sign of another health problem, and should be discussed with your GP if you are experiencing it regularly or if you are taking prescribed medicines that could be a factor. 

Read more about high and low blood pressure.


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