What is blood pressure?
Blood pressure is the pressure of blood in your arteries (blood vessels). Blood pressure is measured in millimetres of mercury (mmHg). Your blood pressure is recorded as two figures. For example, 150/95 mmHg. This is said as '150 over 95'.
What is high blood pressure?
High blood pressure is a blood pressure that is 140/90 mmHg or above each time it is taken. That is, the blood pressure is 'sustained' at 140/90 mmHg or above. High blood pressure can be:
However, it is not quite as simple as this. Depending on various factors, the level at which blood pressure is considered high enough to be treated with medication can vary from person to person.
Blood pressure of 160/100 mmHg or above
This is definitely high. All people with a blood pressure that stays at this level are usually offered medication to lower it (described later).
Blood pressure of 140/90 mmHg or above but below 160/100 mmHg
This is sometimes called 'mild' high blood pressure. Ideally, it should be lower than this but for many people the risk from mild high blood pressure is small, and drug treatment is not indicated. However, certain groups of people with blood pressure in this range are advised medication to lower it. These are people with:
Blood pressure between 130/80 and 140/90 mmHg
For most people this level is fine. However, current UK guidelines suggest that this level is too high for certain groups of people. Treatment to lower your blood pressure if it is 130/80 mmHg or higher may be considered if you:
How is high blood pressure diagnosed?
A one-off blood pressure reading that is high does not mean that you have 'high blood pressure'. Your blood pressure varies throughout the day. It may be high for a short time if you are anxious, stressed, or have just been exercising.
You are said to have 'high blood pressure' (hypertension) if you have several blood pressure readings that are high, and which are taken on different occasions, and when you are relaxed.
Observation period
If one reading is found to be high, it is usual for your doctor or nurse to advise a time of observation. This means several blood pressure checks at intervals over time. The length of the observation period varies depending on the initial reading, and if you have other health risk factors.
For example, say a first reading was mildly high at 150/94. If you are otherwise well, then a period of several months 'observation' may be advised. A blood pressure reading may be taken every few weeks. The observation period is also a good time to change any lifestyle factors that can reduce blood pressure (see below). If the blood pressure readings remain high after an observation period then treatment with medication may be advised, depending on your risk factors (see below).
However, if you have diabetes, or have recently had a heart attack or stroke, you may be advised to have blood pressure checks fairly often over the next week or so. Also, treatment with medication is usually considered at an earlier stage if the readings remain high.
Some people are given (or buy) machines to monitor blood pressure at home (home monitoring) or when they are going about doing their everyday activities (ambulatory monitoring). One reason this may be advised is because some people become anxious in medical clinics which can cause the blood pressure to rise. (This is called 'white coat' hypertension.) Home or ambulatory monitoring of blood pressure may show that the blood pressure is normal when you are relaxed.
What causes high blood pressure?
The cause is not known in most cases
This is called 'essential hypertension'. The pressure in the arteries depends on how hard the heart pumps, and how much resistance there is in the arteries. It is thought that slight narrowing of the arteries increases the resistance to blood flow, which increases the blood pressure. The cause of the slight narrowing of the arteries is not clear. Various factors probably contribute.
In some cases, high blood pressure is caused by other conditions
It is then called 'secondary hypertension'. For example, certain kidney or hormone problems can cause high blood pressure.
How common is high blood pressure?
In the UK, about half of people over 65, and about 1 in 4 middle aged adults, have high blood pressure. It is less common in younger adults. Most cases are mildly high (up to 160/100 mmHg). However, at least 1 in 20 adults have blood pressure of 160/100 mmHg or above. High blood pressure is more common in people:
Do I need any tests?
If you are diagnosed as having high blood pressure then you are likely to be examined by your doctor and have some routine tests which include:
The purpose of the examination and tests is to:
Who should have a blood pressure check?
High blood pressure usually causes no symptoms. You will not know if you have high blood pressure unless you have your blood pressure checked. Therefore, everyone should have regular blood pressure checks at least every 3-5 years. The check should be more often (at least once a year) in: older people, people who have had a previous high reading, people with diabetes, and people who have had a previous reading between 130/85 and 139/89 mmHg (that is, not much below the 'cut off' point for high blood pressure).
Why is high blood pressure a problem if it causes no symptoms?
High blood pressure is a 'risk factor' for developing a cardiovascular disease (such as a heart attack or stroke), and kidney damage, sometime in the future. If you have high blood pressure, over the years it may have a damaging effect to arteries and put a strain on your heart. In general, the higher your blood pressure, the greater the health risk. But, high blood pressure is just one of several possible risk factors for developing a cardiovascular disease.
