High Blood Pressure (Hypertension)

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A guide to high blood pressure, also known as hypertension, 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).

Symptoms of high blood pressure
Causes of high blood pressure
Diagnosing high blood pressure
Treating high blood pressure
Complications of high blood pressure
Preventing high blood pressure


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.

Medication that can help you lower your blood pressure is also available.


Symptoms of high blood pressure

High blood pressure does not usually cause any obvious symptoms. As a result, it is known as the ‘silent killer’.

The only way to find out whether you have high blood pressure is to have your blood pressure checked regularly.

Symptoms can occur in rare cases where a person has a very high blood pressure level. The symptoms may include:

  • a headache
  • blurred or double vision
  • nosebleeds
  • shortness of breath

Visit your GP as soon as possible if you have any of these symptoms.

Regular blood pressure checks

If you are diagnosed with high blood pressure, it is very important to have your blood pressure checked on a regular basis.

Adults who are over 40 and have not been diagnosed with high blood pressure should have their blood pressure checked at least once every five years. However, your blood pressure should ideally be checked more frequently, particularly if you have any contributory risk factors.

Once high blood pressure has been diagnosed, your blood pressure will need to be closely monitored until it is brought under control. After your blood pressure has been controlled, your GP or practice nurse will measure your blood pressure every few months.

Blood pressure checks are usually available on request at most GP surgeries and health clinics. Many also have a policy of arranging regular checks for you. Children usually have their blood pressure routinely tested as part of their regular programme of health checks.


If you are pregnant, you should have your blood pressure checked on a regular basis, even if it is not high.

Watching your blood pressure while you are pregnant reduces your risk of developing pregnancy-induced hypertension, which can lead to a serious condition called pre-eclampsia where there is a problem with the placenta (the organ that links the baby’s blood supply to the mother’s).

Causes of high blood pressure

There are two types of high blood pressure:

  • Primary high blood pressure (also known as essential high blood pressure). There is no identifiable cause for this type of high blood pressure.
  • Secondary high blood pressure, where high blood pressure is caused by an underlying cause, such as kidney disease, or a particular type of medication that you are taking.

Primary high blood pressure

While the specific cause of primary high blood pressure remains unknown, there is compelling evidence to suggest that a number of risk factors increase your chances of developing the condition.
These risk factors include:

  • age – the risk of developing high blood pressure increases as you get older
  • a family history of high blood pressure – the condition seems to run in families
  • being of Afro-Caribbean origin
  • high-fat diet
  • high amount of salt in your diet
  • lack of exercise
  • being overweight
  • smoking
  • excessive alcohol consumption
  • stress

A number of health conditions, such as diabetes and kidney disease, have also been linked to an increase risk of developing primary high blood pressure.

Secondary high blood pressure

Some cases of high blood pressure (between 5 and 10%) are the result of an underlying condition or cause. These include:

  • kidney conditions, such as a kidney infection, or kidney disease
  • narrowing of the arteries
  • hormonal conditions, such as Cushing’s syndrome (a condition where your body produces an excess of steroid hormones)
  • conditions that affect the body’s tissue, such as lupus (a condition where the immune system attacks healthy tissue)
  • medication, such as the oral contraceptive pill, or the type of painkillers that are known as nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen
  • excessive alcohol consumption
  • recreational drugs, such as cocaine, amphetamines and crystal meth

Occasionally, a rise in blood pressure can result from taking oral contraceptives or herbal remedies, such as herbal supplements.

Diagnosing high blood pressure


Blood pressure is often measured using a device that is known as a sphygmomanometer. This device uses an inflatable cuff and has a scale of mercury, like a thermometer.

The cuff is pumped up to restrict the blood flow in your arm, before slowly being released. The person checking your blood pressure will use a stethoscope to listen to your pulse.

Hearing how your pulse reacts after the cuff is released allows a measurement to be taken on the mercury scale, giving an accurate reading of your blood pressure.

Many GP surgeries now use digital sphygmomanometers, which measures your pulse using electrical sensors. Blood pressure testing kits are also commercially available (see box, right).

Before having your blood pressure taken, you should rest for at least five minutes and empty your bladder. To get an accurate blood pressure reading, you should be sitting down and not talking when the reading is taken.

Checking your blood pressure

Having one high blood pressure reading does not necessarily mean that you have high blood pressure. Your blood pressure can fluctuate throughout the day. Feeling anxious or stressed when you visit your GP can raise your blood pressure.

Therefore, your GP will need to take several readings over a set period of time, usually every month, to see whether your blood pressure level is consistently high.

Blood and urine tests may also be carried out in order to check for conditions that are known to cause an increase in blood pressure, such as kidney infections.

You may also be given a blood pressure kit to take home so that you can monitor your blood pressure level throughout the day (see box, left).


The line between normal and raised blood pressure is not fixed. However, it is recommended that the ideal blood pressure should be 120/80mmHg. A normal blood pressure reading is less than 130/80mmHg.

If you have kidney disease, diabetes or a condition that affects your heart and circulation, your target blood pressure should be below 130/80mmHg.

Treating high blood pressure

Treatment for high blood pressure will depend on your blood pressure levels and your associated risk of developing a cardiovascular disease, such as a heart attack or stroke.

There are seven main risk factors for developing a cardiovascular disease. These are:

  • age
  • high blood pressure
  • smoking (or a previous history of smoking)
  • obesity
  • lack of exercise
  • having a high level of cholesterol in your blood
  • having a family history of cardiovascular disease (conditions of the heart or blood vessels)

If your blood pressure is slightly higher than the ideal level (120/80mmHg), and your GP feels that the risks of cardiovascular disease are low, you should be able to lower your blood pressure by making simple lifestyle changes, such as improving your diet and taking regular exercise.

If your blood pressure is moderately high (140/90mmHg or higher), or your GP feels that your risk of developing cardiovascular disease in the next 10 years is more than one in five, you will be prescribed medication and advised about changing your lifestyle.

If your blood pressure is very high (180/110 mmHg or above) you will be referred to a hypertension specialist (a doctor who specialises in treating high blood pressure).

Lifestyle changes

The following lifestyle changes are known to reduce high blood pressure:

  • regular exercise of at least 30 minutes a day, a minimum of five times a week
  • cutting your alcohol intake to recommended levels (less than 21 units a week for men, and less than 14 units a week for women)
  • eating a healthy, low-fat, balanced diet, and restricting your salt intake to less than 6g (0.2oz) a day
  • losing weight if you are overweight or obese
  • restricting your caffeine consumption to less than five cups of coffee or tea a day
  • relaxation therapies, such as yoga and meditation

Be aware that achieving a relatively low decrease in your blood pressure can still have significant health benefits.

See High blood pressure – prevention for more information about how you can change your lifestyle to lower your blood pressure.


A number of different medications can be used to treat high blood pressure. You may need to take more than one type of medication in order to lower your blood pressure because a combination of treatments is sometimes needed to successfully treat the condition.

If you have high blood pressure, you may also need to take blood pressure-lowering medication for the rest of your life. However, if your blood pressure levels stay under control for several years, you might be able to discontinue your treatment.

Most medications that are used to treat high blood pressure have some side effects (see below for details of the specific side effects of each type of medication). Consult your GP immediately if you have any of the following common side effects while taking medication for high blood pressure:

  • feeling drowsy
  • pain around your kidney area (on the side of your lower back)
  • a dry cough
  • dizziness, faintness or light-headedness
  • a skin rash

The most widely used medications for treating high blood pressure are described below.

ACE inhibitors

Angiotensin-converting enzyme (ACE) inhibitors work by blocking the actions of some of the hormones that help to regulate blood pressure. By stopping these hormones from working, the medication helps to reduce the amount of water in your blood, and it widens your arteries. Both of these will decrease your blood pressure.

ACE inhibitors are not suitable for:

  • pregnant or breastfeeding women
  • people with conditions that affect the blood supply to their kidneys
  • people with a history of heart disease

ACE inhibitors have been known to reduce the blood supply to the kidneys, which can reduce their efficiency. Therefore, blood and urine tests may be carried out before you start taking ACE inhibitors to make sure that there are no pre-existing problems with your kidneys.

You may need to have annual blood and urine tests if you continue to use ACE inhibitors.

Side effects of ACE inhibitors include:

  • dizziness
  • tiredness or weakness
  • headaches
  • a persistent dry cough

Most of these side effects should pass in a few days, although some people find that they continue to have a dry cough.

If side effects become particularly troublesome, a medication that works in a similar way to ACE inhibitors, known as an angiotensin-2 receptor antagonist, may be recommended.

ACE inhibitors can cause unpredictable effects if taken with other medications, including some over-the-counter (OTC) ones. Therefore check with your GP or pharmacist before taking anything in combination with this medication.

Calcium channel blockers

Calcium channel blockers work by relaxing the muscles that make up the walls of your arteries. This widens your arteries and reduces your blood pressure.

Calcium channel blockers are not recommended for people with a history of heart disease, liver disease or circulation problems. Side effects of calcium channel blockers include:

  • flushed face
  • headaches
  • swollen ankles
  • dizziness
  • tiredness
  • skin rashes
  • abnormally fast, slow or uneven heart rate

Certain brands of calcium channel blocker may also cause constipation in some people.

However, the side effects that are caused by calcium channel blockers should pass within a few days once your body gets used to the medication.

Do not drink grapefruit juice if you are taking calcium channel blockers because it can lower your blood pressure.

Thiazide diuretics

Thiazide diuretics work by reducing the amount of water in your blood and widening the walls of your arteries. They are not recommended for pregnant women, or people who have gout (a type of arthritis where crystals develop inside the joints).

Thiazide diuretics have been known to reduce the level of potassium in your blood, which can interfere with your heart and kidney functions. They can also raise the level of sugar in your blood, which could lead to diabetes.

Therefore, you will probably be recommended to have blood and urine tests every six months so that your potassium and blood sugar levels can be monitored.

The side effects of thiazide diuretics include:

  • dizziness
  • nausea
  • muscle cramps

A few people have reported that they could not get or maintain an erection while taking thiazide diuretics. However, this particular side effect was resolved once the medication was withdrawn.


Alpha-blockers are effective in reducing high blood pressure. However, they are not usually used unless you are already taking other medication and your blood pressure is still high.

Alpha-blockers work by preventing the muscles that line your blood vessels (alpha receptors) from being activated and tightening the muscles in the walls of your blood vessels. This enables the blood vessels to relax and open, making it much easier for blood to flow through them and lower your blood pressure.

Common side effects of alpha-blockers include:

  • fainting spells when you first start the treatment
  • dizziness
  • headache
  • swollen ankles
  • tiredness


Beta-blockers used to be a popular treatment for high blood pressure, but now they only tend to be used when other treatments have not proved successful. This is because beta-blockers have more potential side effects than the other medications that are used to treat high blood pressure.

Beta-blockers work by slowing down your heart rate and the force of your heart. This reduces the pressure at which the blood is pumped out of your heart and around your body.

Common side effects of beta-blockers include:

  • tiredness
  • nausea
  • cold hands and feet
  • slow heartbeat
  • diarrhoea

Less common side effects of beta-blockers include:

  • sleep disturbances
  • nightmares
  • impotence

Although beta-blockers are not the preferred method of treatment for high blood pressure, they may be considered for younger people if:

  • other treatments, such as ACE inhibitors, have not been effective
  • a woman is fertile (can become pregnant)

Beta-blockers can also interact with other medications, causing possible adverse side effects. Check with your GP or pharmacist before taking other medications in combination with beta-blockers.

Do not suddenly stop taking beta-blockers without first consulting your GP. Stopping this medication suddenly will lead to serious side effects, such as a rise in blood pressure or an angina attack.

Ethnic groups

Research has shown that different blood pressure lowering medications work better for different ethnic groups. For example, ACE inhibitors are more effective as a first-choice medication for treating high blood pressure in white people, whereas calcium channel blockers, or thiazide diuretics, tend to work better for black people.

It is thought that this is because black people tend to have a lower level of renin in their blood. Renin is an enzyme that helps to regulate blood pressure. ACE inhibitors are most effective when there is a high amount of renin in the blood, so they are not as effective in treating black people with high blood pressure.

Therefore, your GP will consider your ethnic background when making a treatment plan.

Complications of high blood pressure

Cardiovascular disease

If left untreated, high blood pressure can cause many different types of cardiovascular disease. For example:

  • stroke- a serious condition where the blood supply to the brain is interrupted
  • heart attack – a serious condition where the blood supply to the heart is blocked
  • blood clot (thrombosis) – a serious condition that is caused by blood clots within the blood vessels
  • aneurysm – a serious condition that is caused by a weakness in the blood vessel wall, which forms a bulge in the blood vessel.

Kidney disease

High blood pressure can damage the small blood vessels in your kidneys and stop them from working properly. This can cause a number of symptoms, including:

  • tiredness
  • swollen ankles, feet or hands (due to water retention)
  • shortness of breath
  • blood and/or protein in your urine
  • urinating more often, particularly at night (nocturia)
  • itchy skin

Kidney disease can be treated using a combination of medication and dietary supplements. More serious cases may require dialysis (a treatment where waste products are artificially removed from the body) or a kidney transplant.

Preventing high blood pressure

The best way of preventing high blood pressure and the associated risks of cardiovascular disease, is to eat a healthy diet, maintain a healthy weight, exercise regularly, drink alcohol in moderation and avoid smoking.


A low-fat, high-fibre diet is recommended, including plenty of fresh fruit and vegetables (five portions a day) and whole grains. Limit the amount of salt that you eat to no more than 6g (0.2oz) a day. Too much salt will increase your blood pressure (6g of salt is about one teaspoonful).

Avoid foods that are high in saturated fat as this will increase your cholesterol level, which is another risk factor for cardiovascular disease.

Foods that are high in saturated fat include:

  • meat pies
  • sausages and fatty cuts of meat
  • butter
  • ghee (a type of butter that is often used in Indian cooking)
  • lard
  • cream
  • hard cheese
  • cakes and biscuits
  • foods that contain coconut or palm oil

However, eating some foods that are high in unsaturated fat can actually decrease your cholesterol level.

Foods that are high in unsaturated fat include:

  • oily fish
  • avocados
  • nuts and seeds
  • sunflower oil, rapeseed oil and olive oil


Drinking excessive amounts of alcohol will increase your blood pressure and raise the cholesterol levels in your blood. Sticking to the recommended amounts of alcohol consumption is the best way to reduce your risk of developing high blood pressure.

The recommended daily limits of alcohol consumption are:

  • 3-4 units of alcohol for men
  • 2-3 units for women

A unit of alcohol is equal to about half a pint of normal-strength lager, a small glass of wine or a pub measure (25ml) or spirits.


It is important to reduce your daily intake of coffee or drinks that contain caffeine, such as soft drinks and cola. Your blood pressure may increase if you drink more than four cups of coffee a day.


Being overweight is a risk factor for having high blood pressure, and your risk increases further if you are obese.

The most scientific way to measure your weight is to calculate your Body Mass Index (BMI). This is your weight in kilograms divided by your height in metres squared. In the UK, people with a BMI of between 25 to 30 are overweight, and those with an index above 30 are classed as obese. People with a BMI of 40 or more are morbidly obese.

The best way to tackle obesity is by reducing the amount of calories that you eat, and taking regular exercise. Your GP can provide you with further information and advice on how you can do this.


Regular exercise will make your heart and blood circulatory system more efficient. It also lowers your cholesterol level and keeps your blood pressure at a healthy level.

For most people, 30 minutes of vigorous exercise a day, at least five times a week, is recommended. The exercise should be strenuous enough to make your heart beat faster, and you should feel slightly out of breath. Examples of vigorous exercise include going for a brisk walk, or walking up a hill.

Relaxation therapies

Relaxation therapies, such as muscle relaxation, stress management and meditation may also help you to reduce your blood pressure.

Support groups

Many support groups, such as The Blood Pressure Association and High Blood Pressure Foundation, offer self-care information and advice for people with high blood pressure.