Hypertension, or high blood pressure, refers to a condition in which the blood pumps around the body at too high a pressure.

In order for a liquid to move forwards there must be a pressure pushing it. This applies especially in the body as part of the circulation of the blood is uphill, against gravity. Thus everybody's blood is pumped around at a pressure and this pressure varies from person to person, and in a single person at different times of day and under different circumstances.

The blood pressure is usually lower when resting or sleeping and needs to be higher during activity. The level that is accepted as "normal" for blood pressure is one which falls within a range based on the average blood pressure of the majority of people. The normal range slowly rises as people grow older.

Hypertension usually causes no noticeable symptoms in itself, but can lead to damage to various organs in the body if the blood pressure remains up for a long time. Over years it can lead to damage to the heart and blood vessels, making it more likely that the individual will develop a stroke or heart attack.

Occasionally, especially when the blood pressure is extremely high, the individual may experience headaches, dizziness, or alterations in vision.

In the majority of cases there is no definite known cause of hypertension. Rarely it can come as a result of kidney disease, glandular (hormone/endocrine) problems, and as a side effect of some medications.

Diagnosis is made by taking the blood pressure which is usually done by a doctor or nurse using a blood pressure machine (sphygmomanometer). This consists of a special cuff which they put around your arm and pump up until the pulse, in the lower arm below the cuff, disappears. The pressure is slowly let out of the cuff, and the professional listens over the artery with a stethoscope for the reappearance of the pulse (the pressure which they hear the beats of the pulse is called the systolic pressure) and the disappearance of the sounds (the pressure at which this happens is called the diastolic pressure). These days an electronic blood pressure machine, which takes the readings automatically, is often used.

The systolic pressure is the maximum pressure the heart achieves as it contracts to force out the blood. The diastolic pressure is the lowest pressure the heart reaches, while it slowly refills before the next contraction.

Although these pressures are measured indirectly they are very close to the actual pressure in the blood vessels or heart. A person's blood pressure alters from minute to minute. It goes up under stress as well as on exercise. Thus a blood pressure (BP) reading taken by the doctor only represents a snapshot and not the whole picture. Many people actually find that their BP goes up as a result of anxiously waiting to see their doctor.

In order to ensure that a truer picture is gained of the overall blood pressure, doctors have traditionally taken readings on a number of successive visits if they find it to be high. Often, after a few attendances, the BP drops to a more normal level.

A more modern way of checking to find the true level is to attach a cuff and measuring device which checks the BP at frequent intervals over 24, or sometimes eight hours. The machine prints out all the results, giving the highs, the lows, and the average (mean). An adjustment has to be made to these readings in order to compare them with blood pressure readings taken in the normal way.

If you have hypertension, your doctor will also want to check to make sure that there is no evidence of any harmful effects on the blood vessels in the back of your eyes, your kidneys, and your heart. This means that your doctor will look in your eyes, examine your heart, and may arrange a chest X-ray and take a tracing of the electrical activity of your heart (electrocardiogram). Your doctor will arrange for a urine specimen to be examined, and a blood test to be taken, to check on the kidneys and your cholesterol level. If other causes are thought to have led to your hypertension, then more tests may be undertaken.

Hypertension is with you for life once the diagnosis is correctly made. Occasionally, marginally raised blood pressure comes back in to the normal range when the patient loses weight, takes more exercise, and cuts down salt intake. If these sort of measures are not successful then drug treatment is necessary, and has been shown to prolong life and cut down the complications of hypertension.

You do need to take your medication if it is prescribed. You may have no symptoms from your high blood pressure, but it will lead to heart attacks and strokes, and other problems too, if left untreated.

From virtually no treatment in 1950, we now have an ever increasing array of effective treatments from which your doctor will choose the most appropriate one for your particular circumstances. As hypertension is generally without noticeable symptoms, the aim is to find a treatment with minimal side effects, because it is important that you are not put off taking your treatment.

• If you are a smoker stop smoking! (Smoking greatly adds to the risk of suffering a heart attack or stroke.)
• If you are overweight, try to lose weight.
• Cut down the salt in your cooking, and do not add salt on the plate.
• Stay active. If possible take at least 30 minutes of continuous exercise three times a week. (One cautionary note is that regular strenuous exercise will bring down blood pressure, but when you stop taking it the blood pressure soon reverts to its previous level.)
• Keep your alcohol intake to less than 28 units of alcohol per week for men or 21 units for women. (In fact one unit per day can help the circulation, but more than this can have negative effects.)
• Stick to healthy food - less fat, more fibre, and plenty of fruit and vegetables.
• You may want to check your own blood pressure, which can help, but try not to become obsessed by this.
• Keep taking your medication, and go for a checkup at regular intervals, as recommended by your doctor.

• Salt: the facts (NHS Choices)
• Reducing the sodium in your diet

Books

Eat to Beat - High Blood Pressure, by Dr Sarah Brewer, Michelle Berridale-Johnson

Natural self help for hypertension, including 60 recipes.

Mayo Clinic on High Blood Pressure, by Dr Sheldon G Sheps

Lifestyle changes to reduce high blood pressure, answers questions on diet, exercise, and medication.

High Blood Pressure at your fingertips, by Professor Tom Fahey, Professor Deirdre Murphy, Dr Julian Tudor Hart

Comprehensive information for anyone with high blood pressure. 3rd edition.

Understanding blood pressure, by Professor D G Beevers

British Medical Association information for patients.

• Omron M10-IT upper arm blood pressure monitor
• Omron R7 wrist blood pressure monitor