Fainting

Also called blackout or syncope (medical term).

Fainting is a sudden, brief (for a few seconds) loss of consciousness. It happens when your brain does not get enough oxygen, causing you to pass out. Most people recover quickly.

Fainting is caused by reduced blood flow to the brain. 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 are in pain. 

Key points about fainting
  1. Fainting is the loss of consciousness for a few seconds. It is also called passing out or blacking out. 
  2. It affects up to 40% (4 in 10) people at least once in their lives.
  3. Fainting can occur at all ages, but most people have their first fainting experience before the age of 40 years.
  4. If you faint for the first time, after the age of 40 years, it is more likely to be due to a serious underlying problem (such as a heart problem, low blood pressure or as a side-effect of medication). Always tell your doctor.
  5. If you feel faint, sit down or lie down. This will lessen the chance of fainting again. Place your head between your knees if you sit down. Don't get up too quickly. Drink plenty of fluids so you don't get dehydrated.

How you might feel before and after fainting

In addition to passing out, you may also feel sick (nauseous) and sweaty. Some people know they are going to faint because they have these symptoms beforehand. You may look pale. You may feel also very tired after you've come round. 

What to do if you feel faint

If you feel faint, sit down or lie down. This will lessen the chance of fainting again. Place your head between your knees if you sit down. Don't get up too quickly. Drink plenty of fluids so you don't get dehydrated.

Possible causes of fainting

Vasovagal reflex

In most cases, common fainting is caused by the vasovagal reflex, where blood pools in the lower body and less blood goes to the brain. This is brought on by:

  • stress or emotional distress
  • pain especially severe pain
  • fear
  • standing for a very long time, especially in hot places 
  • holding your breath.   

Orthostatic hypotension

Fainting can also be caused by a drop in blood pressure when you stand up too fast. This is called orthostatic hypotension and is usually caused by:

  • dehydration
  • after a big meal
  • a side effect of medication such as medication to treat high blood pressure, Parkinson's disease. 

More serious causes

In some cases, fainting may be caused by more serious medical problems such heart or lung problems, stroke, or epilepsy.  

Tests and diagnosis 

See your doctor if you are concerned about a fainting episode/s. To find the cause of fainting, your doctor will do a physical examination and ask questions about the fainting episode. Depending on what the physical examination shows, your doctor may want to do tests such as blood tests, ECG, CT scan of the head. 

Learn more

The following links provide further information on fainting. Be aware that websites from other countries may contain information that differs from New Zealand recommendations.

Faint/Collapse Patient Info, UK