Blood pressure numbers & measurements explained

Lesley Dobson / 01 September 2011 ( 11 May 2017 )

High blood pressure causes half of all strokes and heart attacks. Find out how high your blood pressure is and how to lower it.

According to research by UK charity the Blood Pressure Association, almost three quarters of UK adults are completely unaware of what their blood pressure numbers are.

That’s why the charity is organises Know your Numbers! Week – the nation’s biggest blood pressure testing event, where thousands of venues across the UK, including supermarkets, pharmacies, health clubs and other community venues, offer free blood pressure checks in the second week of September each year.

Are you at risk?

One in three adults in the UK has high blood pressure, but a third of them don’t even know they have it because it’s symptomless. So while many people think they’ll experience warning signs such as headaches or a red face, the reality is the first symptom of high blood pressure can be a stroke or heart attack. High blood pressure is also a risk factor for kidney disease and vascular dementia.

Some may say ignorance is bliss, but this certainly isn’t the case for high blood pressure as, once it’s diagnosed, the condition can be successfully managed. That why it’s so important to have regular blood pressure checks.

While high blood pressure can affect absolutely anyone – young or old, super-fit or couch potato – there are some factors which will increase your risk of developing it:

  • Age – blood pressure tends to rise as we get older. For example, research has found that 20 per cent of those in their 20s have high blood pressure, 40 per cent in their 40s and 60 per cent in their 60s. So it’s increasingly important to have regular checks as you get older. An easy way to do this is to home monitor.
  • Family history – if one or more members of your family (usually a parent or sibling) have high blood pressure then you’ll be at increased risk, and the more family members who have high blood pressure, the greater the risk. If you’ve already been diagnosed with high blood pressure, be sure to pass this information onto your children too.
  • Lifestyle - being overweight, not doing enough exercise, drinking too much alcohol, and eating too much salt and not enough fruit and vegetables can all contribute to high blood pressure.

10 lifestyle changes to help reduce blood pressure

But what do the numbers mean?

Blood pressure measurements are written as two numbers, e.g '120/80' or '120 over 80'. The top number is the systolic, which is when your heart is squeezing and pushing blood around the body, and the bottom number is the diastolic, when your heart relaxes. These numbers are measured in units of millimetres of mercury (or mmHg).

Diastolic vs systolic: what the numbers mean in more detail

We should be all be aiming for a blood pressure of 120/80 or lower, which is the optimal level. Our blood pressure naturally fluctuates throughout the day, but if your readings are consistently at 140/90 or above over a number of weeks (both or just one of the numbers), then you probably have high blood pressure and will need to lower it.

If your readings are between these two levels, then you’d certainly benefit from lowering your blood pressure. A few lifestyle changes could really improve your blood pressure, helping you to avoid developing high blood pressure in the future.

Women must watch blood pressure

It’s often men who are the target of heart disease-related advice, but now middle-aged and older women are being told that the link between raised blood pressure and heart disease is even stronger for them than it is for men.

Researchers from 11 countries worked together on behalf of the International Database on Ambulatory blood pressure in relation to Cardiovascular Outcomes (IDACO), to assess nearly 10,000 people, of whom roughly half were women, over a period of 11 years.

They found that high systolic blood pressure (the first of the two numbers in your reading) is a powerful indicator of the likelihood of heart disease for women. They found that the percentage of potentially preventable and/or reversible cardiovascular disease in men is 24; but for women the figure is a far higher 36%. These figures were based on 24-hour systolic blood pressure monitoring, which gave the researchers a better overview of the participants’ blood pressure than, say, a one-off measurement would have done.

They also discovered that just three risk factors – high systolic pressure, high cholesterol and smoking – account for 85% of reversible risk of heart disease, meaning that if people addressed these issues, the majority of heart problems could be prevented. Analysing the figures further, the researchers calculated that by reducing systolic pressure by just 15mm Hg in hypertensive women, they could expect to see a 40% improvement in terms of preventing cardiovascular disease.

Subtle signs of women's heart disease

Top tips to lower or avoid high blood pressure

Professor Graham MacGregor, Chairman of the Blood Pressure Association, says: "If you’ve been prescribed blood pressure-lowering medicines by your doctor, then it’s really important you take them. Far too many people stop taking their medicines when they see their numbers going down, so their blood pressure goes up again and with this their risk of stroke and heart attack.

"Some people may be put off taking their medicines because of side effects, but the trick is to be persistent with any new medicine, giving your body at least six weeks to adjust if the side-effects aren’t intolerable. If the medicines are still unbearable after this time, then go back to your doctor, as there are literally hundreds of medicines to choose from."

The Blood Pressure Association recommends five top tips to lower blood pressure, which can help some people to avoid developing high blood pressure, and for those already taking medicines, can reduce the amount they need to take:

1. Cut down on salt – no more than 6g a day (a teaspoon), including hidden salt in foods like bread and cereals, so be sure to check labels.

2. Get your 'five a day' of fruit and veg.

3. Stay active – 30 minutes of aerobic activity five times a week.

4. Maintain your ideal weight.

5. Keep an eye on alcohol – no more than 2-3 units a day for women, 3-4 a day for men.

10 signs you're eating too much salt

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