A few readings are needed to diagnose high blood pressure

In the UK, about 1 in 5 people, at least 10 million, have high blood pressure - or hypertension.Because it is a silent disease, many people are unaware that they are affected.

Others that do know are not receiving the right treatment, experts say.

BBC News Online looks at why treating high blood pressure is important

What is blood pressure?

Blood pressure is the force exerted by blood on the walls of the arteries when the heart beats.

What is 'high' blood pressure?

When measured, two readings are recorded. The first is called the systolic pressure which represents the force of the blood as the heart contracts (beats) to pump it around the body.

The second, called the diastolic pressure, is the pressure whilst the heart is filling with blood again in preparation for the next heart beat. For most people a blood pressure reading less than 140/90 is desirable.

How do I know if I have high blood pressure?

All adults should have their blood pressure checked at least once every five years, but preferably more often. This is especially true as you get older, as blood pressure goes up with age.

Your GP can measure your blood pressure using a machine. Unless your blood pressure is very high, you will be asked to have readings taken several times.

This is to make sure that you really do have high blood pressure, rather than high blood pressure because you are nervous at the doctors, or have rushed to get to your appointment for example.

Why is high blood pressure dangerous?

The higher your blood pressure, the greater your risk of developing narrowed arteries which can lead to heart problems, kidney disease and strokes.

The good news is that if your blood pressure is high, it can be lowered by making changes to your lifestyle, such as changing your diet, exercising and losing weight, and when needed, with tablets.

What causes high blood pressure?

For most people there is no definite cause for their high blood pressure and doctors call this essential hypertension.

A small number of people have what is called secondary hypertension, which means that there is an underlying cause of their high blood pressure.

This could be problems with the kidneys or adrenal glands, which sit above your kidneys. These glands produce hormones that are important in controlling blood pressure.

Who gets high blood pressure?

• It can affect anyone, but some groups of people are more likely to have it:

• People with high blood pressure in the family

• Older people - blood pressure increases with age

• People with unhealthy lifestyles - smoking, obesity, poor diet, little exercise and excess alcohol

• People with other conditions like diabetes, heart disease or kidney problems

• Some ethnicities - Afro Caribbean, South Asian

How is it treated?

This will depend on how high it is and on what other 'risk factors' you have for heart disease and stroke, such as high cholesterol or diabetes.

You will probably be asked to make some changes to your lifestyle.

This may include losing some weight, taking up regular exercise, cutting down on alcohol and eating more fruit and vegetables.