It's known as the ‘silent killer’ because although it typically has no symptoms, high blood pressure can cause potentially fatal damage to your heart and arteries.

But the condition which affects one in three UK adults doesn't have to be a killer, as it can be reduced and controlled through lifestyle measures and medication.

Mind you, that’s easier said than done.

At least a third of the 16 million Britons with high blood pressure (also known as hypertension) don't know they have it. This month is May Measurement Month, a global initiative led by two organisations representing the world’s leading cardiologists and researchers specialising in hypertension — the International Society of Hypertension and the World Hypertension League - encouraging people to be more aware of their blood pressure and what they need to do to reach and maintain a healthy blood pressure.

Prevention is always better

A spokesperson from Blood Pressure UK, explains why people need to get their blood pressure checked.

[Read more: 6 healthy numbers you need to know]

“There's no better treatment for raised blood pressure than prevention. The sooner you can find out what your blood pressure is, and can take steps to reduce it, the better. Knowing your numbers could save your life.”

Changes are easy

“Simple changes such as eating less salt, losing weight, eating more fruit and vegetables and taking exercise have been proven to reduce blood pressure and lower your risk of having a stroke or a heart attack.

But the risks of not changing are huge…

High blood pressure is the main risk factor for stroke and a major risk factor for heart attack, heart failure and kidney disease.

People with high blood pressure are three times more likely to develop heart disease and stroke and twice as likely to die from them as people with normal blood pressure. Indeed, Blood Pressure UK says 62,000 unnecessary deaths from stroke and heart attacks occur every year due to poor blood pressure control.

There's also increasing evidence that it's a risk factor for vascular dementia.

So what exactly is high blood pressure?

High blood pressure is a level consistently at or above 140mmHg and/or 90mmHg, and if your blood pressure is repeatedly measured at this level or above, the pressure may be putting strain on your blood vessels.

This strain can clog up, narrow or weaken the vessels, and also lead to clots, damaging the heart or brain. It can also lead to blood vessels bursting, although this is rare.

And the symptoms?

High blood pressure rarely has any symptoms, so the only way to know if you have the condition is to have your blood pressure regularly measured.

Blood Pressure UK recommends all adults should have a blood pressure check at least once a year – although if you've already been diagnosed with high blood pressure, you should have it checked more often. This can be done at your GP's, many pharmacies, gyms and sometimes even your workplace. Home blood pressure monitors are also available.

[Read more: High blood pressure: Your questions answered]

What do the readings mean?

A single high reading doesn't necessarily mean you have high blood pressure, as many things can affect your readings through the day. Because of this, your doctor will take a number of readings over several weeks to see if your blood pressure stays high over time.

If your blood pressure readings remain high, changing your diet and being more active can help bring it under control. However, they may not lower it enough on their own, and you may need to take blood pressure medication to lower it further.

Who’s most at risk?

While anyone can get high blood pressure, it’s far more common as you get older - more than half of people over the age of 75 have the condition. And as well as lifestyle factors such as being overweight, a poor high-salt diet, lack of exercise and drinking too much making high blood pressure more likely, you're also more at risk if you have a family history of high blood pressure, stroke or heart attack.

For more information on blood pressure and to find a screening site during May Measurement Month, head to www.maymeasure.org or ask your local pharmacist.