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Blood pressure ranges explained - and how to measure yours

By Joanna Pearl

Find out about measuring blood pressure, including systolic and diastolic readings, and how to use a blood pressure monitor.

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At Which? we test arm and wrist blood pressure monitors in lab conditions to find the best blood pressure monitors that offer the accurate measurements you need, and the models that can't be relied on despite their large price tags.

This page gives you the vital basic advice to make sure you're really suitable for home blood pressure testing, what health conditions should make you think twice before buying, and what your blood pressure measurement is telling you.

Take a look at our blood pressure monitor Best Buys to discover the models that Which? recommends.

What is a blood pressure range?

When you use a blood pressure monitor to take your blood pressure, you are measuring the pressure of your blood against the walls of your arteries as your heart pumps it round your body.

Your blood pressure range is measured in millimetres of mercury (mmHg), and is recorded as systolic and diastolic figures.

• Systolic pressure – this is the pressure of the blood when your heart pushes it out.
• Diastolic pressure – this is the pressure of the blood when your heart is resting between beats.

So if your GP tells you that your blood pressure is '130 over 90', or 130/90mmHg, you have a systolic pressure of 130mmHg and a diastolic pressure of 90mmHg.

What's your ideal blood pressure?

Your blood pressure reading should ideally be below 120/80mmHg. However, anything under 130/80mmHg is generally considered a normal reading.

You are said to have high blood pressure (sometimes called hypertension) if separate readings consistently show your blood pressure to be 140/90mmHg or higher. If you have kidney disease, diabetes or another condition affecting your heart and circulation, your target blood pressure should be below 130/80mmHg.

If you need to monitor your blood pressure at home, we are unique in putting blood pressure monitors through ease of use tests, and letting you know which ones don't offer you the accuracy you need based on our rigorous tests in clinic conditions.

Be aware of what can raise your blood pressure as you take a home reading: even having a full bladder or crossing your legs can increase it.

Find out which models have earned our Best Buy blood pressure monitor recommendations from brands including Omron.

Should I be using a home blood pressure monitor?

Using a home blood pressure monitor can help you monitor your day-to-day blood pressure rather than just taking it in clinic conditions where you may be more anxious, which could affect your readings.

It can allow you to build up a picture of your blood pressure range over time and share this with your health professional. It can also help you to see how new treatments are working for you.

However, it can make some people more anxious. So it’s important to discuss with a health professional, such as your GP, whether it’s the right thing for you.

How can I tell if a blood pressure monitor will give accurate results?

You can check the model's box to see if it has passed international standard clinical tests. This information is also available from the British Hypertension Society.

However, the British Hypertension Society doesn’t rate usability, as Which? does, and it doesn't publish the details of monitors that have not met international testing criteria.

In our lab tests we found seven Don't Buy blood pressure monitors that we don't think will measure your blood pressure accurately. And price isn't a good indicator, as the inaccurate models revealed by our tests cost as much as £80.  

How should I prepare for taking a blood pressure reading?

When you use your monitor you should be seated with your arm stretched out and supported, on the arm of a chair or a cushion, for example. You should be quiet and relaxed, sitting for five minutes before you take the reading, and not too hot or cold.

Make sure you follow the manufacturer's instructions exactly - for example, if they tell you to position the tube down the centre of your arm in line with your middle finger, that's precisely what you need to do to get accurate readings.

And make sure you have wrist monitors at the specified height - it’s trickier to hold your wrist monitor in the right position than an arm monitor, making the readings more prone to inconsistencies.

What health conditions might make me think twice before buying a monitor?

There are certain groups of people who might have particular needs, including:

• Pregnant women should check that the monitor they are thinking of buying is validated for use in pregnancy – not all are.
• People with atrial fibrillation or other arrhythmias should not rely on an automated blood pressure monitor to give accurate measurements.

People in either of these categories should discuss this with their doctor or nurse before buying.

What else can I do to bring my blood pressure down?

You can help prevent or reduce high blood pressure by eating healthily, maintaining a healthy weight, regular exercise, drinking alcohol in moderation and not smoking.

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