The only way to know if you have high blood pressure (hypertension) is to have your blood pressure checked.
This can be done by your GP or another healthcare professional, or you can check it yourself with a home testing kit.
Healthy adults aged over 40 should have their blood pressure checked at least once every five years and yearly over the age of 60 years.
If you are at an increased risk of high blood pressure, you should have your blood pressure checked more often, ideally once a year.
Getting checked by your GP
Blood pressure checks are usually available on request at most GP surgeries and health clinics.
Blood pressure is often measured using a sphygmomanometer, a device which consists of a stethoscope, arm cuff, dial, pump and valve.
The cuff is placed around your arm and pumped up to restrict the blood flow. The pressure is then slowly released as your pulse is checked using the stethoscope.
Hearing how your pulse beats 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 measure your pulse using electrical sensors.
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.
Blood pressure readings
Having one raised blood pressure reading does not necessarily mean you have high blood pressure. 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 period of time, usually every month, to see if your blood pressure level is consistently high.
You may also have blood and urine tests to check for conditions that are known to cause an increase in blood pressure, such as kidney disease.
You may be given a blood pressure kit to take home so you can monitor your blood pressure level throughout the day.
Increasingly doctors use 24 hour blood pressure monitors that automatically check your blood pressure every 30 minutes to 1 hour. These devices are thought to be more accurate that Sphygmomanometers and can provide additional useful data to your doctor about blood pressure while you sleep and how your blood pressure varies throughout the day.
Home testing kits
Portable testing kits that measure your blood pressure at home or on the move can be a useful way of getting a more accurate reading.
This is because some people become anxious in medical clinics, which can cause the blood pressure to rise, a condition called white coat hypertension.
Home or portable blood pressure monitoring kits may show that your blood pressure is in fact normal when you are relaxed.
You can buy a variety of testing kits so you can monitor your blood pressure at home or while you're out and about.
It is important to buy a blood pressure monitor that is reliable and gives accurate readings and to take advice from an expert on how to use it.
Understanding your reading
Blood pressure measures how strongly blood presses against the walls of your arteries (large blood vessels) as it is pumped around your body by your heart.
It is measured in millimetres of mercury (which is written as mmHg) and it is recorded as two figures:
- systolic pressure: the pressure of the blood when your heart pushes blood out
- diastolic pressure: the pressure of the blood when your heart rests in between beats
For example, if your GP says your blood pressure is '140 over 90', or 140/90mmHg, it means you have a systolic pressure of 140mmHg and a diastolic pressure of 90mmHg.
Ideally, your blood pressure reading should be below 120/80mmHg. However, anything under 130/80mmHg is generally considered normal.
You are said to have high blood pressure if readings on separate occasions consistently show your blood pressure to be 140/90mmHg or higher.
If you have kidney disease, diabetes or a condition that affects your heart and circulation, your target blood pressure should be below 130/80mmHg.
Find out how to treat high blood pressure.
Your blood pressure reading
Ideally, your blood pressure reading should be below 120/80mmHg.
However, anything under 140/90mmHg is generally considered normal.