Blood pressure is a measure of the force that your heart uses to pump blood around your body.
Blood pressure is measured in millimetres of mercury (mmHg) and is given as two figures:
For example, if 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.
As a general guide:
High blood pressure is often related to unhealthy lifestyle habits, such as smoking, drinking too much alcohol, being overweight and not exercising enough.
Left untreated, high blood pressure can increase your risk of developing a number of serious long-term health conditions, such as coronary heart disease and kidney disease.
Low blood pressure is less common. 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.