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High blood pressure (hypertension)

What is high blood pressure? What do the numbers really mean, and why is it so important to 'Know Your Numbers'?

What is blood pressure?

In your body, it’s the force with which blood flows through your arteries, the blood vessels that carry blood from your heart to the rest of your body.

It’s helpful to think of blood pressure like the force of water flowing through a hose.

Blood pressure is measured using two numbers:

  • Systolic pressure: this is the higher of the two numbers. It’s the pressure against your arteries when your heart is pumping blood around your body.
  • Diastolic pressure: this is the lower of the two numbers. It shows how much pressure is in your arteries when your heart relaxes between beats.

They're both measured in millimetres of mercury (mmHg).

Blood Pressure Chart

Understanding your numbers

Once you know your numbers, you can use the blood pressure chart to see what they mean and if your blood pressure is in the healthy range. The chart is suitable for adults of any age, as the cut-off point for diagnosing high blood pressure doesn’t change with age.

Simply find your top number (systolic) on the left side of the chart and your bottom number (diastolic) on the bottom. Where the two lines meet is your blood pressure.

As a general guide:

  • high blood pressure is considered to be from 140/90mmHg or more if your reading was taken at a GP surgery or clinic (or an average of 135/85mmHg if it was taken at home)
  • if you're over the age of 80, high blood pressure is considered to be from 150/90mmHg or more if your reading was taken at a GP surgery or clinic (or an average of 145/85mmHg if it was taken at home)
  • ideal blood pressure is usually considered to be between 90/60mmHg and 120/80mmHg, while the target for people over the age of 80 years old is below 150/90mmHg (or 145/85mmHg if it was taken at home)

Blood pressure readings from 121/81mmHg to 139/89mmHg could mean you're at risk of developing high blood pressure if you do not take steps to keep your blood pressure under control.

Everyone's blood pressure will be slightly different. What's considered low or high for you may be normal for someone else.

If you have a recent blood pressure reading use the NHS Check your blood pressure tool to understand what your reading means. You'll also get information about what to do next.

Treating high blood pressure

Simple lifestyle changes can help reduce high blood pressure, although some people may need to take medicine as well.

Your GP can advise you about changes you can make to your lifestyle and discuss whether they think you'd benefit from medicine.

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Preventing high blood pressure


High blood pressure can often be prevented or reduced by eating healthily, maintaining a healthy weight, taking regular exercise, drinking alcohol in moderation and not smoking.