Blood pressure is a measure of the force that your heart uses to pump blood around your body.
It is measured using a blood pressure monitor, which calculates readings consisting of two numbers.
The top number on a blood pressure monitor represents systolic pressure – which is the force at which your heart pumps blood around the body.
The bottom number on a blood pressure monitor represents diastolic pressure – which is the resistance to the blood flow in the blood vessels.
Both systolic and diastolic pressure are measured in millimetres of mercury.
So if your blood pressure reads 140 over 90, or 140/90mmHg, it means you have a systolic pressure of 140mmHg and a diastolic pressure of 90mmHg.
According to the NHS, ideal blood pressure is considered to be between 90/60mmHg and 120/80mmHg.
High blood pressure is considered to be 140/90mmHg or higher, and low blood pressure is considered to be 90/60mmHg or lower.
A blood pressure reading between 120/80mmHg and 140/90mmHg could mean you’re at risk of developing high blood pressure if you don’t take steps to keep your blood pressure under control, said the NHS.
High blood pressure, or hypertension, can be dangerous, as if left untreated it could increase your risk of having a heart attack or stroke, as well as heart disease and heart failure.
It can also increase your risk of getting peripheral arterial disease, aortic aneurysms, kidney disease and vascular dementia.
High blood pressure is often related to unhealthy lifestyle habits, such as smoking, drinking too much alcohol, being overweight and not exercising enough.
According to the NHS, more than one in four adults in the UK have high blood pressure, but many won’t realise it.
Symptoms are hard to notice, so the only real way to find out if your blood pressure is too high is to have your blood pressure checked.
Low blood pressure, or hypotension, is less common than high blood pressure. Some medications can cause low blood pressure as a side effect.
It can also be caused by a number of underlying conditions, including heart failure and dehydration.
Low blood pressure doesn’t always cause symptoms, but you may need treatment if it does.
Symptoms include: lightheadedness or dizziness, feeling sick, blurred vision, generally feeling weak, confusion and fainting.
If you get symptoms when you stand up or suddenly change position, you may have postural hypotension.
“All adults over 40 are advised to have their blood pressure checked at least every five years. Getting this done is easy and could save your life,” said the NHS.
You can get your blood pressure checked at your GP surgery, some pharmacies, as part of your NHS Health Check and in some workplaces.
You can also check your blood pressure yourself with a home blood pressure monitor.