If you have high blood pressure you probably won't feel ill or have any symptoms. But high blood pressure increases your chance of having a heart attack or a

 

 

 

 

 

stroke
You have a stroke when the blood supply to a part of your brain is cut off. This damages your brain and can cause symptoms like weakness or numbness on one side of your body. You may also find it hard to speak if you've had a stroke.

 

 

 

 

 

stroke. It can also lead to

 

 

 

 

 

kidney disease
Kidney disease refers to conditions in which the kidneys (the organs in the body that make urine) have been damaged. Kidney disease can result from a number of different causes, including hypertension, which puts too much pressure on the kidneys.

 

 

 

 

 

kidney disease and

 

 

 

 

 

heart failure
When the heart loses its ability to push enough blood through the circulation, it is called heart failure.

 

 

 

 

 

heart failure.

The good news is that there are many things you can do to lower your blood pressure. You can change your lifestyle, for example, or take medications.

Your doctor may call high blood pressure hypertension.

To understand why you have high blood pressure and how treatments work, it helps to know a bit about how blood flows through your body and what controls the pressure.

You need a certain amount of pressure to keep blood moving through your blood vessels. When your heart beats it pushes blood out and around your body. This causes the pressure to rise. When the heart relaxes and fills with blood, the pressure drops.

There are two parts to the blood pressure reading.

There are three main things that help control blood pressure:

 

 

 

 

 

Source:
Beevers G, Lip GYH, O'Brien E (editors).
ABC of hypertension.
4th edition. BMJ Books, London, UK; 2001.

 

 

 

 

 

¹

These three things are controlled by:

 

 

 

 

 

Source:
Beevers G, Lip GYH, O'Brien E (editors).
ABC of hypertension.
4th edition. BMJ Books, London, UK; 2001.

 

 

 

 

 

¹

The amount of pressure your blood needs to be under to keep flowing varies slightly from one minute to the next. It depends on how much oxygen and food the various organs in your body need. When you exercise, your muscles need lots of oxygen and your heart has to pump faster, so your blood pressure may rise.

If your body senses that your blood pressure is too low to meet its demands, the brain sends messages through nerves to the heart to tell it to pump faster and harder.

This pushes more blood out and around the body with each beat, and the blood surges through the arteries under higher pressure.

If your body senses that your blood pressure is too high, the brain sends messages through another nerve to slow down the heart. Your body also releases chemicals to open up (dilate) the arteries so blood can flow through easily without putting extra pressure on the walls of your blood vessels. Your blood pressure then drops.

The system works a bit like a garden hose. If you turn on the tap full, the water shoots out through the narrow hose under high pressure. As you turn off the tap the pressure drops.

Your kidneys control how much fluid is in your blood vessels, so they have a role in controlling blood pressure. To learn more, see How your kidneys help control your blood pressure.

It's normal for your blood pressure to rise and fall throughout the day. But if it stays high for a long time (usually for at least four months), then it's called high blood pressure.

Usually your doctor will say you have high blood pressure if your blood pressure reading has been at least 140 (top number) or over 90 (bottom number) on at least two occasions.

 

 

 

 

 

Source:
National Institutes of Health, National Heart, Lung and Blood Institute National High Blood Pressure Education Program.
The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.
Available at http://www.nhlbi.nih.gov/guidelines/hypertension/jnc7full.pdf (accessed on 17 January 2008).

 

 

 

 

 

² This is written as 140/90.

To learn more, see What the numbers tell you.

No one knows exactly what goes on in your body to cause high blood pressure. But researchers think that you get it when the balance of certain chemicals in the blood is upset. These chemicals control how fast your heart beats, how open the arteries are and how much blood there is in your blood vessels. If the balance of chemicals is upset:

All these things can make your blood pressure rise.

 

 

 

 

 

Source:
Beevers G, Lip GYH, O'Brien E (editors).
ABC of hypertension.
4th edition. BMJ Books, London, UK; 2001.

 

 

 

 

 

¹

Your doctor probably won't be able to tell you why you have high blood pressure. More than 9 in 10 people with high blood pressure never know the exact cause.

But researchers do know that some people are more likely to get high blood pressure than others. Doctors call the things that increase your chance of getting a condition risk factors. The most well-known risk factors for getting high blood pressure are:

To find out more, see Risk factors explained.

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