Fainting happens when your brain doesn't get enough oxygen, causing you to pass out. Most people recover quickly.
Fainting is caused by reduced blood flow to the brain, often due to low blood pressure. After you lose consciousness (pass out) and fall or lie down, more blood can flow to your brain so you wake up again. Usually fainting happens for a reason, such as if you have been standing for a long time in a hot place, or if you're in pain.
Before you faint, you might experience a range of symptoms or warnings. These can include:
- looking pale
- feeling warm
- feeling light-headed, sick (nauseous) and sweaty
- experiencing a spinning sensation
- losing some or all of your vision
- having trouble hearing.
Some people know they are going to faint because they have these symptoms beforehand, this is known as pre-syncope.