High blood pressure: how it is found, what causes it and what treatment involves

What does a blood pressure reading mean?

Blood pressure is the force of blood against the walls of the arteries. A reading gives two numbers: the pressure when the heart beats and the pressure between beats. The site's page on blood pressure measurement explains how they are taken.

Doctors use different thresholds for readings taken in a clinic and for readings taken at home when deciding whether blood pressure is high.

Does high blood pressure cause symptoms?

Usually not. The NHS says high blood pressure often has no symptoms, so many people do not know they have it, and the only way to find out is to have it measured. Rarely it can cause headaches, blurred vision or chest pain.

Over time, the NHS says, untreated high blood pressure raises the chance of problems such as stroke and heart disease.

What causes it?

For most people there is no obvious cause, which is called essential hypertension, and it can run in families. In a small number of people there is an underlying cause, such as a kidney or adrenal gland condition.

The NHS says risk rises with age, with Black African or Black Caribbean ethnicity, and with a family history. Smoking, drinking too much alcohol, being overweight and not being active are also linked.

The NHS advises calling NHS 111 for frequent headaches or blurred vision, chest pain that comes and goes, or other symptoms thought to come from high blood pressure.

How is the diagnosis confirmed?

A single clinic reading is usually followed by other checks. NICE advises confirming raised clinic readings with home monitoring or with a 24-hour ambulatory monitor, which takes readings through the day.

Some people have higher readings in a clinic than at home, sometimes called the white coat effect, which is one reason these extra checks are used. A GP may also arrange blood and urine tests and an ECG, which checks the heart rhythm.

A reading taken in a clinic is less accurate than home or ambulatory readings and is not enough on its own to diagnose high blood pressure.

What does treatment involve?

Lifestyle changes come first for many people. The NHS lists cutting down on salt and alcohol, being more physically active, losing weight where needed, and stopping smoking.

A GP will usually prescribe medicine if blood pressure is very high, if the person has a higher risk of heart attack or stroke, or if it stays high after lifestyle changes. Several types are used, including ACE inhibitors, angiotensin receptor blockers, calcium channel blockers and diuretics, and the choice depends on things such as age and ethnicity.

Some people need to take blood pressure medicine long term, though if blood pressure stays under control for several years it may be possible to cut back or stop treatment.

Most blood pressure medicines are taken as tablets.

Making lifestyle changes early on may mean some people can avoid needing medicine.

Water tablets (diuretics) work by increasing the amount of salt the kidneys remove.

When is it an emergency?

The NHS says to call 999 for sudden chest pain that does not go away, or chest pain with sweating, sickness, light-headedness or breathlessness, as it could be a heart attack.

NHS guidance for pharmacy staff says a very high clinic reading together with symptoms such as headache, palpitations, new confusion or chest pain should be referred to A&E, using 999 where necessary.