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If you are with someone who is unconscious, call triple zero (000) for an ambulance, and if the person stops breathing, start CPR.

Key facts

  • A blackout is a temporary loss of consciousness.
  • Blackouts can be caused by fainting, low blood pressure, or something more serious.
  • If you have a blackout, it’s best to see your doctor.

What is a blackout?

A blackout is a temporary loss of consciousness. It may also be called:

  • fainting (syncope)
  • a collapse
  • passing out

If a blackout is caused by alcohol or drug use, you may experience memory loss.

If you have a blackout, it may not be serious. But it’s still important to see your doctor to try and work out what is causing the blackouts.

What symptoms are related to blackouts?

If you have a blackout, you lose consciousness temporarily. Before that, you may:

What causes a blackout?

There are many different causes of blackouts, such as:

  • a problem with your cardiovascular system
  • a problem within the brain
  • the effects of drugs or alcohol

One common cause of a blackout is fainting. Fainting occurs when your heart rate drops and your blood vessels widen. This results in low blood pressure. It can happen when you:

  • are very hot
  • are distressed
  • are in pain
  • see or smell something unpleasant
  • are coughing
  • are going to the toilet

Sometimes, you might black out when you stand up too quickly. This is because your blood pressure suddenly drops.

Some medicines can also trigger blackouts.

Blacking out can also be caused by more serious health conditions, including:

Blackouts caused by alcohol

Sometimes, people experience memory loss after drinking a lot of alcohol. They may describe this as a blackout.

If you drink a lot of alcohol, you may not remember what happened when you sober up. This is because the brain can’t form new memories when the alcohol in your blood reaches a certain level. The more you drink, the more memory you lose.

You are more likely to black out from alcohol if you:

  • drink on an empty stomach
  • drink too much too quickly

To avoid blacking out from alcohol, you can manage your alcohol intake. Make sure you:

  • drink slowly and don’t drink too much
  • take sips of water between sips of alcohol
  • eat food while you drink
  • avoid binge drinking

Drinking so much that you black out can cause physical, social and mental problems. It can lead to:

  • accidents and injuries
  • violent behaviour
  • long-term health issues
  • alcohol poisoning

When should I see a doctor?

If you have blacked out and you don’t know why, you should seek medical attention. It could be a sign that something is seriously wrong.

This is very important if you also have:

  • a family history of fainting
  • a family history of heart problems
  • chest pain
  • heart palpitations

If you see someone blackout, take these steps:

  • raise their legs above the level of their head
  • get medical help

If you are with someone who is unconscious, call triple zero (000) for an ambulance, and if the person stops breathing, start CPR.

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How are blackouts diagnosed?

If you have a blackout, your doctor will try to find the cause. They may conduct:

  • a physical examination
  • blood pressure testing
  • blood tests to check your blood sugar levels
  • an electrocardiogram (ECG)
  • an echocardiogram
  • an exercise stress test
  • tilt table testing

How are blackouts treated?

Treatment will depend on the cause of your blackout.

For example, blackouts caused by cardiac (heart) problems may be treated by a heart specialist. Other treatments may include:

  • fluids
  • medicines
  • advice on lifestyle changes

First aid for blackouts

There are things you can do if you feel like you are going to blackout.

If you feel faint, “go-to-ground”. This means you should get as close to the ground as possible, to avoid injury when you blackout.

Once you are on the ground, lie down with your feet higher than your head. If you can’t do this, sit with your head between your knees.

If you can, position yourself in a cool, quiet space.

Can blackouts be prevented?

As blackouts are caused by different conditions, it’s not always possible to prevent them.

You can help stop a blackout from happening by:

  • changing position slowly
  • staying hydrated
  • eating well
  • getting fresh air
  • avoiding triggers such as hot showers, and standing or lying down for too long

Complications of blackouts

If you have had a blackout, it’s best not to drive a vehicle until you have recovered.

If you blackout, you may also be at risk of injury from falling over.

Resources and Support

You can call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with 24 hours a day, 7 days a week.

If you need help with alcohol, visit:

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: May 2023

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