Blood pressure is a measure of the force that the blood applies to the walls of the arteries as it flows through them. It's normal for blood pressure to increase when you exert yourself, or when you feel stressed or anxious. But if your blood pressure is consistently higher than normal at rest, this is high blood pressure, also known as hypertension.
About 3 in 10 adults have high blood pressure in the UK. It is much more common in older people - 7 out of 10 people in their 70s have high blood pressure.

Blood pressure
Blood is pumped around the body by the heart carrying oxygen and nutrients. As a result of the pumping action of the heart and the size and flexibility of the arteries that carry blood, the blood is under pressure. This blood pressure is an essential and normal part of the way the body works.

High blood pressure develops if:
• the walls of your larger arteries lose their elasticity and become rigid
• the small blood vessels become narrower

Measuring blood pressure
Blood pressure is measured with a monitor called a sphygmomanometer. This is a digital box attached to a tube with a cuff on the end. The cuff is placed around the upper arm and inflated to a certain level, then deflated slowly. A sensor in the cuff provides information about the blood pressure or a doctor or nurse will listen to the blood flow using a stethoscope.
The result is expressed as two numbers, such as 120/80 mm HG ("one hundred and twenty over eighty millimetres of mercury").
• The top figure - the systolic blood pressure - is a measure of the pressure when your heart muscle is contracting and pumping blood. This is the maximum pressure in your blood system.
• The bottom figure - the diastolic blood pressure - is the pressure between heart beats when the heart is resting and filling with blood. This is the minimum pressure in your blood system.
In the UK, high blood pressure is defined as a consistently increased systolic blood pressure of 140 or over and/or a diastolic blood pressure of 85 or over. If your blood pressure is around this level, your doctor will probably want to monitor it regularly.
If you suffer from diabetes, it is even more important that your blood pressure is lower than this - ideally less than 130/80.

Types of high blood pressure
Primary hypertension
More than 9 in 10 people with high blood pressure have what's called 'primary' or 'essential hypertension'. This means that there's no single clear cause of it.
Although the exact cause of high blood pressure isn't fully understood, it's known that some factors to do with your lifestyle can contribute. These include:
• smoking
• your family history
• obesity (being very overweight)
• drinking a lot of alcohol - especially if you binge drink
• a lack of exercise
• your diet

Secondary hypertension
Around 5 in 10 people with high blood pressure have 'secondary hypertension'. This means your condition can be linked to a recognised cause - in fact, it may be a symptom of another underlying disease or factor such as:
• kidney disease
• endocrine disease
• narrowing of the aorta
• steroid medicines
• the contraceptive pill
• pregnancy, which can cause pre-eclampsia
Symptoms
Most people with high blood pressure don't have any symptoms.
People with severe high blood pressure or a rapid rise in blood pressure may also experience headaches, blurred or impaired vision, fits or black-outs.

Complications
People with high blood pressure have an increased risk of major illnesses including:
• cardiovascular disease such as angina, stroke, heart attack or atrial fibrillation
• kidney damage
• damaged sight

Diagnosis
As most people with high blood pressure don't have any symptoms, they are diagnosed when they have their blood pressure taken as part of a medical examination. That's one good reason to have a regular check-up with your doctor, especially if you're over 50.
Your doctor may request that you come back for repeat measurements over a number of weeks before suggesting that you have treatment. This is so he or she can check that the high reading is an ongoing problem and not a one-off.
You may also need some tests to see if high blood pressure is having an effect on the rest of your body. These may include:
• an analysis of your urine (protein in your urine may be the first sign of a kidney problem)
• a blood test, to check your cholesterol and blood sugar levels as well as the condition of your kidneys
• an ECG (electrocardiogram), which records the electrical changes happening in your heart

Monitoring
24-hour ambulatory monitoring
You may need 24-hour testing to measure your blood pressure over 24 hours. A monitoring device will be strapped round your waist and it will be attached to a cuff wrapped around your upper arm. The cuff will inflate and deflate throughout the 24 hours and take blood pressure recordings.

Blood pressure monitors
You might consider getting a blood pressure monitor to use yourself at home - discuss this option with your doctor, who should be able to help you choose a suitable one. The Blood Pressure Association (see Further information) also has advice and a list of suppliers.
It is important to take readings on different days - for example you should not just measure yourself when you feel stressed. Set days in the week to take the measurement so that you can get an objective reading.
You should continue to get your blood tested regularly by your doctor even if you use a blood pressure monitor at home.

Treatment
Slightly raised blood pressure may not need to be treated so aggressively, but regular monitoring is important.
If you have very severe high blood pressure, you may need to go to hospital for treatment. But it's much more likely that you will be cared for by your GP and/or a nurse.

Lifestyle changes
First, your doctor or nurse is likely to discuss lifestyle changes which might help lower your blood pressure. He or she might, for example, advise you to:
• stop smoking - for more information on quitting smoking please see the separate BUPA factsheet, Giving up smoking
• change your diet to a low fat, low salt diet that includes fruit and vegetables - for more information about healthy diet, please see the separate BUPA factsheet, Healthy eating
• cut down on alcohol
• get some regular moderate exercise - for more information, please see the separate BUPA factsheet, Physical activity
• lose any excess weight
It may also help to try to reduce the stress in your life to avoid short-term rises in blood pressure - try relaxation techniques or meditation.

Drug treatments
If your blood pressure remains high, your doctor may prescribe you one or more of the following antihypertensive drugs.
• ACE inhibitors or angiotensin II receptor antagonists (eg ramipril, losartan) - these make the walls of the blood vessels relax and widen.
• Calcium channel blockers (eg amlodipine) or alpha blockers (eg doxazosin) - these help widen the blood vessels.
• Diuretics (eg bendroflumethiazide) - these increase the amount of water and salt removed from your blood by your kidneys. This triggers hormones which lower blood pressure.
• Beta-blockers (eg atenolol) - these drugs reduce the work your heart has to do, by reducing your pulse rate at times when it may beat too forcefully such as during exercise or when you are feeling stressed.
The drugs you are prescribed will depend on a number of factors, including your age and ethnicity. It may take time to find the best treatment for you, balancing the benefits against any side-effects.
It is important to be committed to taking your medication every day as most people don't have any symptoms from high blood pressure.

Further information
• Blood Pressure Association
020 8772 4994

• The British Heart Foundation
08450 70 80 70