Use the blood pressure chart below to see what your blood pressure means. The blood pressure chart is suitable for adults of any age. (The level for high blood pressure does not change with age.)

Blood pressure readings have two numbers, for example 140/90.

The top number is your systolic blood pressure. (The highest pressure when your heart beats and pushes the blood round your body.) The bottom one is your diastolic blood pressure. (The lowest pressure when your heart relaxes between beats.)

The blood pressure chart below shows ranges of high, low and healthy blood pressure readings.

You probably have high blood pressure (hypertension) if your blood pressure readings are consistently 140 over 90, or higher, over a number of weeks.

You may also have high blood pressure if just one of the numbers is higher than it should be over a number of weeks.

If you have high blood pressure, this higher pressure puts extra strain on your heart and blood vessels. Over time, this extra strain increases your risk of a heart attack or stroke.

High blood pressure can also cause heart and kidney disease, and is closely linked to some forms of dementia.

What are the signs and symptoms of high blood pressure?

High blood pressure usually has no signs or symptoms, so the only way to know if you have high blood pressure is to have yours measured. However, a single high reading does not necessarily mean you have high blood pressure. Many things can affect your blood pressure through the day, so your doctor will take a number of blood pressure readings to see that it stays high over time.
Occasionally people with very high blood pressure say they experience headaches, but it is best to visit your GP if you are concerned about symptoms.

What causes high blood pressure?

For most people, there may be no single cause for their high blood pressure. We do not know exactly what causes high blood pressure. We do know that your lifestyle can affect your risk of developing it. You are at a higher risk if:

• you eat too much salt;
• you don’t eat enough fruit and vegetables;
• you are not active enough;
• you are overweight; or
• you drink too much alcohol.

You can help to lower your blood pressure - and your risk of stroke and heart attack - by making lifestyle changes.

Additional causes of high blood pressure

There are some factors that increase your risk of developing high blood pressure, which you cannot control. These include:

• Age: as you get older, the effects of an unhealthy lifestyle can build up and your blood pressure can increase.
• Ethnic origin: people from African-Caribbean and South Asian communities are at greater risk than other people of high blood pressure.
• Family history: you are at greater risk if other members of your family have, or have had, high blood pressure.

Some people may have high blood pressure that is linked to another medical condition, such as kidney problems. For these people treating the medical problem may lower their blood pressure back to normal.

More on Treatments for High Blood Pressure.

Some people have a blood pressure level that is lower than normal. In general this may be good news - because the lower your blood pressure is, the lower your risk of stroke or heart disease. However, in a few cases, having low blood pressure can cause problems, so you might need to speak to your doctor or nurse.

What is a low blood pressure reading?

A low blood pressure reading is having a level that is 90/60mmHg, or lower.

Only one of the numbers has to be lower than it should be to count as low blood pressure. In other words:

• if the top number is 90 or less (regardless of the botton number) this may be low blood pressure
• if the bottom number is 60 or less (regardless of the top number) this may be low blood pressure.

What causes low blood pressure?

Some people have a blood pressure level that is naturally low. That is, there is no specific cause or reason why.

However, some health conditions or medicines can cause you to develop low blood pressure.

Is low blood pressure dangerous?

Usually, having low blood pressure is not a cause for concern. However, sometimes your blood pressure can drop to a point where you may feel faint or dizzy.

If you find that your blood pressure is suddenly much lower than usual, there may be a reason for this. Speak to your doctor or nurse.

How is low blood pressure treated?

Most people with low blood pressure will not need treatment.

If your doctor or nurse feels that you would benefit from treatment, they will often try to find a cause for your low blood pressure. If they can find the cause, they should be able to decide on the most appropriate treatment for you.