In most cases, it's not clear exactly what causes high blood pressure (hypertension). But there are several things that can increase your risk.

Who's at risk of high blood pressure

Factors that can raise your risk of developing high blood pressure include:

• age – the risk of developing high blood pressure increases as you get older
• a family history of high blood pressure
• being of African or Caribbean origin
• a high amount of salt in your food 
• lack of exercise
• being overweight
• regularly drinking large amounts of alcohol
• smoking
• long-term sleep deprivation

Making healthy lifestyle changes can help keep your blood pressure at a normal level.

Find out more about how to prevent high blood pressure

Known causes of high blood pressure

In about 1 in 20 cases, high blood pressure happens as the result of an underlying health condition or taking a certain medicine.

Health conditions that can cause high blood pressure include:

• kidney disease
• diabetes
• long-term kidney infections
• obstructive sleep apnoea – where the walls of the throat relax and narrow during sleep, interrupting normal breathing
• glomerulonephritis – damage to the tiny filters inside the kidneys
• narrowing of the arteries supplying the kidneys
• hormone problems – such as an underactive thyroid, an overactive thyroid, Cushing's syndrome, acromegaly, increased levels of the hormone aldosterone (hyperaldosteronism), and phaeochromocytoma
• lupus – a condition in which the immune system attacks parts of the body, such as the skin, joints and organs
• scleroderma – a condition that causes thickened skin, and sometimes problems with organs and blood vessels

Medicines that can increase your blood pressure include:

• the contraceptive pill
• steroids
• non-steroidal anti-inflammatory drugs (NSAIDs) – such as ibuprofen and naproxen
• some pharmacy cough and cold remedies
• some herbal remedies – particularly those containing liquorice
• some recreational drugs – such as cocaine and amphetamines
• some selective serotonin-noradrenaline reuptake inhibitor (SSNRI) antidepressants – such as venlafaxine

In these cases, your blood pressure may return to normal once you stop taking the medicine or drug.

High blood pressure (hypertension) does not usually have any symptoms, so the only way to find out if you have it is to get your blood pressure checked.

Healthy adults aged over 40 should have their blood pressure checked at least once every 5 years.

If you're at an increased risk of high blood pressure, you should have your blood pressure checked more often, ideally once a year.

Having this done is easy and could save your life.

Where to get a blood pressure test

You can ask for a blood pressure check. You do not have to wait to be offered one.

Blood pressure testing is available:

• at your GP surgery – by a GP, practice nurse, healthcare assistant or self-service machine
• at some pharmacies
• at an NHS Health Check appointment offered to adults aged 40 to 74 in England
• in some workplaces
• at a health event

You can also test your blood pressure at home using a home testing kit.

Having a blood pressure test

A stethoscope, arm cuff, pump and dial was normally used to measure your blood pressure, but automatic devices with sensors and digital displays are commonly used nowadays.

It's best to sit down with your back supported and legs uncrossed for at least 5 minutes before the test.

You'll usually need to roll up your sleeves or remove any long-sleeved clothing so the cuff can be placed around your upper arm.

Try to relax and avoid talking while the test is carried out.

During the test:

• you hold out one of your arms so it's at the same level as your heart, and the cuff is placed around it – your arm should be supported in this position with a cushion or the arm of a chair, for example 
• the cuff is pumped up to restrict the blood flow in your arm – this squeezing may feel a bit uncomfortable, but only lasts a few seconds
• the pressure in the cuff is slowly released and detectors sense vibrations in your arteries – a doctor will use a stethoscope to detect these if your blood pressure is measured manually
• the pressure in the cuff is recorded at 2 points as the blood flow starts to return to your arm – these measurements are used to give your blood pressure reading

You can usually find out your result straight away, either from the healthcare professional carrying out the test or on the digital display.

If your blood pressure is high, you may be advised to record your blood pressure at home to confirm whether you have high blood pressure.

Ambulatory (24-hour) blood pressure monitoring

Having a raised blood pressure reading in 1 test does not necessarily mean you have high blood pressure.

Blood pressure can fluctuate throughout the day. Feeling anxious or stressed when you visit your GP can also raise your blood pressure.

If you have a high reading, you may be asked to take some readings with a home blood pressure monitor, or wear a 24-hour monitor that checks your blood pressure throughout the day.

This will confirm whether you have consistently high blood pressure.

It's known as 24-hour or ambulatory blood pressure monitoring.

Home blood pressure testing

Blood pressure tests can also be carried out at home using your own blood pressure monitor.

Like 24-hour or ambulatory monitoring, this can give a better reflection of your blood pressure.

It can also allow you to monitor your condition more easily in the long term.

You can buy a variety of low-cost monitors so you can test your blood pressure at home or while you're out and about.

Measure your blood pressure twice a day, ideally in the morning and the evening, while you're sitting down.

Each time take 2 readings, 1 minute apart. Continue to measure your blood pressure twice a day for 7 days.

Your doctor or nurse will use this information to work out your average blood pressure.

It's important to make sure you use equipment that's been properly tested.

The British Hypertension Society (BHS) has information about validated blood pressure monitors that are available to buy.

Understanding your blood pressure reading

Blood pressure is measured in millimetres of mercury (mmHg) and is given as 2 figures:

• systolic pressure – the pressure when your heart pushes blood out
• diastolic pressure – the pressure when your heart rests between beats

For example, if your blood pressure is "140 over 90", or 140/90mmHg, it means you have a systolic pressure of 140mmHg and a diastolic pressure of 90mmHg.

As a general guide:

• high blood pressure is considered to be 140/90mmHg or higher (or an average of 135/85mmHg at home) – or 150/90mmHg or higher (or an average of 145/85mmHg at home) if you're over the age of 80
• ideal blood pressure is usually considered to be between 90/60mmHg and 120/80mmHg, while the target for over-80s is below 150/90mmHg (or 145/85mmHg at home)

Blood pressure readings between 120/80mmHg and 140/90mmHg could mean you're at risk of developing high blood pressure if you do not take steps to keep your blood pressure under control.

Simple lifestyle changes can help reduce high blood pressure, although some people may need to take medicine as well.

Your GP can advise you about changes you can make to your lifestyle and discuss whether they think you'd benefit from medicine.

This patient decision aid (PDF, 132kb) can also help you to understand your treatment options.

When treatment is recommended

Everyone with high blood pressure is advised to make healthy lifestyle changes.

Whether medicine is also recommended depends on your blood pressure reading and your risk of developing problems such as heart attacks or strokes.

Your doctor will carry out some blood and urine tests, and ask questions about your health to determine your risk of other problems:

• if your blood pressure is consistently above 140/90mmHg (or 135/85mmHg at home), but your risk of other problems is low – you'll be advised to make some changes to your lifestyle
• if your blood pressure is consistently above 140/90mmHg (or 135/85mmHg at home) and your risk of other problems is high – you'll be offered medicine to lower your blood pressure, in addition to lifestyle changes
• if your blood pressure is consistently above 160/100mmHg – you'll be offered medicine to lower your blood pressure, in addition to lifestyle changes

Lifestyle changes

There are some changes you could make to your lifestyle to reduce high blood pressure.

Some of these will lower your blood pressure in a matter of weeks, while others may take longer.

Try to:

• cut your salt intake to less than 6g (0.2oz) a day, which is about a teaspoonful – find out how you can reduce the amount of salt in your diet
• eat a low-fat, balanced diet – including plenty of fresh fruit and vegetables; get tips on eating more healthily
• be active – read some tips about getting more exercise
• cut down on alcohol – get tips on cutting down, including downloading a drinks diary and keeping track of your drinking
• lose weight – find out what your ideal weight is using the BMI healthy weight calculator and read advice about losing weight if you're overweight
• drink less caffeine – found in coffee, tea and cola
• stop smoking – get help quitting

You can take these steps today, regardless of whether or not you're taking blood pressure medicines.

In fact, by making these changes early on you may be able to avoid needing medicines.

Get more advice about lifestyle changes to prevent and reduce high blood pressure

Medicines for high blood pressure

Several types of medicine can be used to help control high blood pressure.

Many people need to take a combination of different medicines.

• if you're under 55 years of age – you'll usually be offered an ACE inhibitor or an angiotensin-2 receptor blocker (ARB)
• if you're aged 55 or older, or you're any age and of African or Caribbean origin – you'll usually be offered a calcium channel blocker

You may need to take blood pressure medicine for the rest of your life. But your doctor might be able to reduce or stop your treatment if your blood pressure stays under control for several years.

It's really important to take your medicine as directed. If you miss doses, it will not work as well.

The medicine will not necessarily make you feel any different, but this does not mean it's not working.

Medicines used to treat high blood pressure can have side effects, but most people do not get any.

If you do get side effects, do not stop taking your medicine. Talk to your doctor, who may advise changing your medicine.

ACE inhibitors

Angiotensin-converting enzyme (ACE) inhibitors reduce blood pressure by relaxing your blood vessels.

Common examples are enalapril, lisinopril, perindopril and ramipril.

The most common side effect is a persistent dry cough. Other possible side effects include headaches, dizziness and a rash.

Angiotensin-2 receptor blockers (ARBs)

ARBs work in a similar way to ACE inhibitors. They're often recommended if ACE inhibitors cause troublesome side effects.

Common examples are candesartan, irbesartan, losartan, valsartan and olmesartan.

Possible side effects include dizziness, headaches, and cold or flu-like symptoms.

Calcium channel blockers

Calcium channel blockers reduce blood pressure by widening your blood vessels.

Common examples are amlodipine, felodipine and nifedipine. Other medicines, such as diltiazem and verapamil, are also available.

Possible side effects include headaches, swollen ankles and constipation.

Drinking grapefruit juice while taking some calcium channel blockers can increase your risk of side effects.

Diuretics

Sometimes known as water pills, diuretics work by flushing excess water and salt from the body through your pee.

They're often used if calcium channel blockers cause troublesome side effects.

Common examples are indapamide and bendroflumethiazide.

Possible side effects include dizziness when standing up, increased thirst, needing to go to the toilet frequently, and a rash.

You might also get low potassium and low sodium after long-term use.

Beta blockers

Beta blockers can reduce blood pressure by making your heart beat more slowly and with less force.

They used to be a popular treatment for high blood pressure, but now tend to be used only when other treatments have not worked.

This is because beta blockers are considered less effective than other blood pressure medicines.

Common examples are atenolol and bisoprolol.

Possible side effects include dizziness, headaches, tiredness, and cold hands and feet.

High blood pressure in older people

The target blood pressure reading for the over-80s is below 150/90 mmHg when it's measured in the clinic or surgery, and below 145/85 mmHg for home readings.

While there are definite benefits from taking medicines to reduce blood pressure if you're under the age of 80, it's less clear it's useful if you're over 80.

It's now thought that if you reach 80 while you're taking medicine for high blood pressure, it's fine to continue treatment provided it's still helping you and is not causing side effects.

If you're diagnosed with high blood pressure and you're aged over 80, your doctor will also consider your other health risk factors when deciding whether to give you treatment for the high blood pressure.

High blood pressure can often be prevented or reduced by eating healthily, maintaining a healthy weight, taking regular exercise, drinking alcohol in moderation and not smoking.

Healthy diet

Cut down on the amount of salt in your food and eat plenty of fruit and vegetables. 

The Eatwell Guide highlights the different types of food that make up our diet, and shows the proportions we should eat them in to have a well-balanced and healthy diet.

Salt raises your blood pressure. The more salt you eat, the higher your blood pressure. Aim to eat less than 6g (0.2oz) of salt a day, which is about a teaspoonful.

Find out how to cut down on salt

Eating a low-fat diet that includes lots of fibre, such as wholegrain rice, bread and pasta, and plenty of fruit and vegetables also helps lower blood pressure.

Aim to eat 5 portions of fruit and vegetables every day.

Find out how to get your 5 A Day

Limit your alcohol intake

Regularly drinking too much alcohol can raise your blood pressure over time.

Staying within the recommended levels is the best way to reduce your risk of developing high blood pressure:

• men and women are advised not to regularly drink more than 14 units a week
• spread your drinking over 3 days or more if you drink as much as 14 units a week

Find out how many units are in your favourite drink and get tips on cutting down.

Alcohol is also high in calories, which will make you gain weight and can further increase your blood pressure.

Find out how many calories are in popular drinks

Lose weight

Being overweight forces your heart to work harder to pump blood around your body, which can raise your blood pressure.

Find out if you need to lose weight with the BMI healthy weight calculator

If you do need to lose some weight, it's worth remembering that just losing a few pounds will make a big difference to your blood pressure and overall health.

Get tips on losing weight safely

Get active

Being active and taking regular exercise lowers blood pressure by keeping your heart and blood vessels in good condition.

Regular exercise can also help you lose weight, which will also help lower your blood pressure.

Adults should do at least 150 minutes (2 hours and 30 minutes) of moderate-intensity aerobic activity, such as cycling or fast walking, every week.

Physical activity can include anything from sport to walking and gardening.

Get more ideas on how to get active

Cut down on caffeine

Drinking more than 4 cups of coffee a day may increase your blood pressure. 

If you're a big fan of coffee, tea or other caffeine-rich drinks, such as cola and some energy drinks, consider cutting down.

It's fine to drink tea and coffee as part of a balanced diet, but it's important that these drinks are not your main or only source of fluid.

Stop smoking

Smoking does not directly cause high blood pressure, but it puts you at much higher risk of a heart attack and stroke.

Smoking, like high blood pressure, will cause your arteries to narrow.

If you smoke and have high blood pressure, your arteries will narrow much more quickly, and your risk of heart or lung disease in the future is dramatically increased.

Get help to stop smoking