It is where blood pressure in your arteries is abnormally low, according to the NHS.
They state that someone with hypotension has a reading under 90/60.
Since it restricts the amount of blood flowing to vital organs, it can cause unsteadiness, dizziness or fainting.
Other symptoms include blurred vision, nausea, confusion, heart palpitations and general weakness.
The NHS recommend that if you experience symptoms you should stop what you are doing, lie down and drink some water.
They should pass after a few seconds or minutes.
If they are frequent, you should see your GP so they can help identify an underlying cause.
There are particular types of hypotension.
Postural hypotension is when you stand up suddenly and experience symptoms.
This tends to affect people as they get older, and can lead to falls.
Postprandial hypotension, however, is when symptoms hit after eating – usually because your intestines need a large amount of blood for digesting, causing pressure to drop.
The third type is neutrally mediated hypotension which can happen after standing for long periods, and it usually affects children and young adults.
Hypotension has many possible causes including hot temperatures, eating large meals and stress.
Some research has also suggested it could be inherited.
According to Parkinson’s UK, low blood pressure may also be a symptom of Parkinson’s disease.
Treatment options for hypotension include standing up gradually, avoiding caffeine at night and eating smaller meals frequently.