Basic Information on High Blood Pressure

{SCA} High blood pressure, also known as hypertension, is usually defined as having a sustained blood pressure of 140/90mmHg or above. Blood pressure is measured in millimetres of mercury, or mmHg (see below for a more detailed explanation).

High blood pressure often causes no symptoms, or immediate problems, but it is a major risk factor for developing a serious cardiovascular disease (conditions that affect the functioning of the heart and the circulation of blood around the body), such as a stroke or heart disease.

The Heart

The heart is a muscle that is designed to constantly pump blood around the body. The heart pumps blood that is low in oxygen towards the lungs, where it receives a fresh supply of oxygen. Once the blood is fully oxygenated, the heart pumps the oxygen-rich blood around the body so that the oxygen can be used by the body’s muscles and cells.

Blood pressure

Two measurements are used to measure blood pressure:

  • Systolic pressure is the measure of blood pressure exerted when your heart beats and forces blood around your body.
  • Diastolic pressure is the measure of blood pressure when your heart is resting in between beats.

Blood pressure is defined as the amount of pressure that is exerted on the artery walls as blood moves through them.

Both the systolic and diastolic pressures are measured in millimetres of mercury (mmHg). The figures are usually represented with the systolic pressure first, followed by the diastolic pressure. Therefore, if your GP says that your blood pressure is ‘120 over 80’, or 120/80mmHg, they mean that you have a systolic pressure of 120mmHg and a diastolic pressure of 80mmHg.

If you have high blood pressure, your heart has to work harder to pump blood around your body. Over time, this can weaken it. The increased pressure can also damage the walls of your arteries, resulting in a blockage or causing the artery to split (haemorrhage). Both of these situations can cause a stroke.

How common is high blood pressure?

High blood pressure is a common condition, affecting around one in three adults in England. It is estimated that 18% of adult men and 13% of adult women have high blood pressure but are not getting treatment for it.

The risk of developing high blood pressure increases with age. Half of people over 75 years have the condition.

For reasons that are not fully understood, people of Afro-Caribbean origin are more likely to develop high blood pressure than other ethnic groups.


High blood pressure is a major risk factor for developing cardiovascular diseases such as:

  • coronary heart disease – where the main arteries that supply your heart (the coronary arteries) become clogged up with plaques (fatty deposits)
  • strokes – a serious condition where the blood supply to your brain is interrupted
  • heart attacks – a serious condition where the blood supply to your heart is blocked

Diabetes and kidney disease are also linked to high blood pressure. See High blood pressure – complications for more information about it.

In 90-95% of cases, there is no single identifiable reason for a rise in blood pressure. But all available evidence shows that lifestyle plays a significant role in regulating your blood pressure. Risk factors for high blood pressure include:

  • age
  • poor diet
  • lack of exercise
  • being overweight
  • excessive alcohol consumption

High blood pressure can be treated or prevented by making changes to your lifestyle, such as eating a healthier diet, exercising more regularly, and reducing the amount of alcohol that you drink.