Diagnosing low blood pressure 

Low blood pressure (hypotension) can be easily diagnosed by measuring your blood pressure. You may need further tests, such as blood tests or an electrocardiogram (ECG), to determine the underlying cause.

Blood pressure testing is available in a variety of settings:

  • at your GP surgery – by a GP, practice nurse, healthcare assistant or self-service machine
  • at a pharmacy
  • as part of your NHS Health Check
  • in some workplaces
  • at a health event
  • at home – you can check blood pressure yourself with a home testing kit

Healthy adults aged over 40 should have their blood pressure checked at least once every five years.

How blood pressure is measured

Blood pressure is often measured using a sphygmomanometer, a device that 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.

A measurement is 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.

Postural or orthostatic hypotension

If your symptoms of low blood pressure mostly occur when you suddenly move into a more vertical position, your blood pressure may be measured before and after you move. For example, your blood pressure may be measured while you are sitting down and again while you are standing up.

Depending on what your seated blood pressure is, if your systolic reading falls by between 15 to 30mmHg when you stand up, you may have orthostatic hypotension (also known as postural hypotension).

Understanding your blood pressure reading

Blood pressure is measured in millimetres of mercury (mmHg) and is recorded as two figures:

  • systolic pressure (the top number) – the pressure of the blood when your heart pushes blood out
  • diastolic pressure (the bottom number) – the pressure of the blood when your heart rests in between beats, which reflects how strongly your arteries are resisting blood flow

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.

As a general guide, low blood pressure is a reading below 90/60. If you have low blood pressure according to this guide, you don't need to worry. Naturally low blood pressure rarely causes symptoms or needs treatment. Having low blood pressure is considered healthy because it protects you from the risks and diseases of high blood pressure.

Page last reviewed: 22/05/2015

Next review due: 22/05/2017