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3 December 2021

Blood pressure ranges explained - and how to measure yours

Find out about measuring blood pressure, including systolic and diastolic readings, and how to use a blood pressure monitor.
CW
Christina Woodger
Woman using arm blood pressure monitor

If you're shopping for a blood pressure monitor, we can lend a helping hand. In our jargon-busting guide, we explain how to make sure you're 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.

At Which?, we test arm and wrist blood pressure monitors in lab conditions to find the best blood pressure monitors that offer accurate measurements, and the models that can't be relied on despite their hefty prices. Once you've used our expert reviews to find the best blood pressure monitor, the next step is to master using it.

Keep scrolling for more details on blood pressure range and tips on how to prepare before taking a reading.

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

Blood pressure range explained

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 around your body.

Your blood pressure range is measured in millimeters of mercury (mmHg) and is recorded as systolic and diastolic figures. But what's the difference?

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

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.

According to advice on the NHS website, a blood pressure reading between 120/80mmHg and 140/90mmHg could mean you're at risk of developing high blood pressure. To avoid this, you need to take steps to keep your blood pressure under control.

What Is considered a normal blood pressure range?

Your blood pressure reading should ideally be below 120/80mmHg. However, anything between 90/60mmHg and 120/80mmHg is defined as ideal or 'normal' blood pressure.

People with ideal blood pressure are at a much lower risk of heart disease and stroke. If you commit to a healthy lifestyle, you'll be able to maintain this level.

What causes high blood pressure?

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.

High pressure can potentially put a strain on your arteries and organs, so it's worth consulting a medical professional who can help you lower your blood pressure to an ideal level.

But remember, blood pressure levels will vary throughout the day. If you record a single high reading, take follow-up readings over the next couple of days to see if you notice any changes.

There are various reasons why you may have high blood pressure. Your lifestyle plays an important role – being overweight, drinking and smoking can all raise your blood pressure. 

What you eat also has an impact on your blood pressure. In fact, according to Blood Pressure UK, eating foods that are high in sugar can make you put on weight, which raises your blood pressure. Too much saturated fat can raise blood cholesterol.

What causes low blood pressure?

Low blood pressure isn't as serious as high blood pressure, but it's still worth addressing as it can cause dizziness and fainting.

Some people have a naturally low blood pressure that doesn't cause any problems – genes can play a role. Low pressure may also be caused by an illness or health issue such as diabetes, neurological conditions, heart problems, or serious injury and shock.

The NHS website suggests you try the following to ease low blood pressure symptoms: 

  • Get up slowly from sitting to standing
  • Take care when getting out of bed
  • Eat small but frequent meals
  • Increase the amount of water that you drink each day
  • Try to avoid sitting or standing for long periods
  • Do not drink caffeinated drinks at night
  • Do not drink too much alcohol

Ultimately, if you're worried about low blood pressure, your first step should be to contact a medical professional for further advice.

How to lower blood pressure

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

When deciding how to change your diet, pay close attention to the food labels at your local supermarket – you want to cut your salt intake (the NHS recommends less than 6g a day) and stick to low-fat foods including fresh fruit and vegetables.

How to monitor your blood pressure at home

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 – that could affect your readings.

A home blood pressure monitor can allow you to build a timeline so you can share results with your health professional. It can also help you see how new treatments are working for you and what impact they're having on your body.

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.

When shopping for a blood pressure monitor, you should check to see if the model has passed international standard clinical tests. This information is also available from the British Hypertension Society. There are certain groups of people who might have particular needs:

  • 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 with their doctor or nurse before buying.

If you need to monitor your blood pressure at home, note that Which? expert blood pressure monitor reviews measure ease of use for every model. In other words, we'll let you know which blood pressure monitors aren't as accurate as you need them to be.

Using an arm monitor

How to take a blood pressure reading

When you use your blood pressure 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.

To help you shop savvy, we've put together an in-depth guide on how to buy the best blood pressure monitor