High blood pressure

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High blood pressure rarely has any symptoms

What is high blood pressure?

If your blood pressure is consistently higher than it should be it is called high blood pressure or hypertension.

There are two main types of high blood pressure:

  • Secondary hypertension: when the change in blood pressure comes as a result of (or secondary to) a specific disease or defect. This is rare and is caused by conditions such as kidney disease, problems with glands that produce hormones, and congenital problems affecting a blood vessel in the heart or brain.
  • Essential or primary hypertension: this is the type of high blood pressure that most people have. With primary hypertension there is no specific disease process involved and there is likely to be no single cause.

High blood pressure is not a disease in itself. However, it can lead to an increased risk of heart disease and strokes.

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Measuring blood pressure

Blood pressure is measured in millimetres of mercury (mmHg) and is recorded as two readings:

  • Systolic pressure (higher reading): records the pressure within the blood vessels as the heart contracts and forces blood out into the arteries.
  • Diastolic pressure (lower reading): records the pressure when the heart fills up with blood again.
The only way to know what your blood pressure is is to have it measured

The only way to know what your blood pressure is is to have it measured

These readings are recorded for example as 120 / 80mmHg.
The only way to know what your blood pressure is is to have it measured

Traditionally, blood pressure was measured using an instrument called a sphygmomanometer (also known as a 'sphyg'). This method used a column of mercury as a scale.

Nowadays electronic devices are often used to measure blood pressure. With an electronic device a cuff is wrapped around your arm; it is set to automatically inflate / deflate and an electronic reading is taken. These devices do not use mercury but the reading is based on the same principle and means the same thing.

What is normal blood pressure?

Most doctors agree that the ideal blood pressure is around 120 / 80mmHg.

The aim is to keep your blood pressure as close to the 'target range' as possible:

  • This is currently 140 / 90mmHg or less.
  • If you have diabetes the lower target range of 130 / 80mmHg is used.
  • If you are aged over 80 years the higher target range of 150 / 90mmHg is used
  • If your blood pressure is within this range you have a lower risk of heart disease and stroke.

Your blood pressure is considered to be low if it is less than 90 / 60mmHg. Some people naturally have a low blood pressure; other people may have low blood pressure as a result of illness or treatment.

What causes high blood pressure?

Primary hypertension is usually a result of a number of factors, known as risk factors. Some risk factors you cannot control, such as your age, family history or ethnic origin.

Other risk factors, which can contribute to high blood pressure, are to do with the way you lead your life. These include:

  • Smoking
  • A high salt intake
  • Being overweight
  • How active you are
  • How much alcohol you drink
  • How you cope with stress

Making changes to these lifestyle factors can significantly reduce high blood pressure in some people, improve your overall health and reduce your risk of heart disease and strokes.

How will I know if I have high blood pressure?

  • High blood pressure very rarely has any symptoms. The only way to know your blood pressure reading is to have it measured. High blood pressure is more common as you get older so having it checked regularly is very important.
  • A one-off high measurement is not enough to make a diagnosis of high blood pressure. You may have your blood pressure closely monitored by your doctor or he / she may want you to monitor your blood pressure at home over a short period of time.
  • If you have been diagnosed with high blood pressure you will need a thorough check-up to look for any signs of damage (e.g. to your eyes or kidneys) and to look for any possible causes. Your may also need some tests / investigations.
Atheroma build up in a coronary artery causing a restricted blood flow

Atheroma build up in a coronary artery causing a restricted blood flow

Why is high blood pressure dangerous?

Even though high blood pressure often has no symptoms it can lead to serious problems throughout your body. Over the years high blood pressure slowly damages your blood vessels, making them narrower and more rigid. This means that:

  • Your heart has to work harder to push the blood through your vessels and your overall blood pressure rises
  • It's easier for clots to get caught and for fatty debris (atheroma) to block your blood vessels


Without careful monitoring and treatment high blood pressure can cause:

  • Angina and heart attacks due to damaged or blocked vessels in the heart
  • Heart failure as the heart has to work much harder
  • Strokes due to damage to the blood vessels in the brain
  • Kidney failure due to damage to the arteries in the kidneys
  • Vision problems and blindness due to damaged blood vessels in the eyes

Because high blood pressure puts you at increased risk of heart disease or stroke your doctor may do a cardiovascular (CVD) risk assessment. This will help your doctor decide what treatment is best for you.

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