The day after drinking alcohol a person may experience symptoms known as a hangover. The main cause of a hangover is the toxic effects of ethanol.

What is a hangover?

When you have a hangover it’s your body trying to protect itself from alcohol’s toxic effects.  

A hangover is when your body is:

  • Clearing toxic by-products of alcohol
  • Rehydrating
  • Healing tissues
  • Restoring normal functioning

A hangover can begin within hours of the last drink as your blood alcohol level  begins to drop. The more you drink, the more likely you are to experience a hangover. 

Hangover symptoms

Hangover symptoms

The severity of hangover symptoms depends on many factors. Hangover symptoms can last up to 24 hours after alcohol has left the blood.1 They usually peak when your blood alcohol level drops to zero. Common hangover symptoms include:

  • Headache
  • Dry mouth
  • Fatigue
  • Stomach pain 
  • Diarrhoea and nausea
  • Trouble concentrating
  • Tiredness and trembling
  • Increased heart rate and blood pressure
  • Anxiety
  • Poor or decreased sleep

What causes hangover symptoms?

When the body breaks down alcohol, it creates acetaldehyde, a highly toxic chemical and known carcinogen. High levels of acetaldehyde in the body can cause symptoms commonly associated with a hangover:

  • Headaches
  • Nausea 
  • Vomiting
  • Increased heart rate
  • Facial flushing

In the long-term, this process can cause permanent damage at the cellular level and lead to cancer.

Alcohol triggers an inflammatory response from your immune system. This can impact:

  • Appetite
  • Concentration
  • Memory
  • Weakened immune system

Alcohol is a diuretic which makes you urinate more, which can lead to dehydration. Short-term effects include: 

  • Headaches
  • Dizziness
  • Thirst
  • Fatigue

While some people might fall asleep more quickly after drinking, you are less likely to get the sleep you need to wake feeling refreshed. 

Alcohol can cause our sleep to be broken or shallow, which can lead to intensify hangover symptoms and cause fatigue, brain fog, and low mood.

Alcohol irritates and inflames the stomach and intestine lining which can cause:

  • Nausea
  • Vomiting
  • Diarrhea
  • Heartburn
  • Acid reflux

In the long-term, this can lead to chronic inflamed lining (gastritis), stomach ulcers and digestive problems. 

What is ‘hangxiety’?

It’s common for people to have increased feelings of anxiety after drinking alcohol. Although it’s not a diagnosed medical condition, this is often referred to as ‘hangxiety’, and generally occurs during the hangover period. 

While drinking alcohol can give you a short-lived feeling of relaxation, alcohol disrupts chemicals and processes in the brain which can both cause and worsen feelings of anxiety, worry, and agitation the next day. 

A hangover is your body's way of saying you drank too much.

Prevent getting a hangover by drinking less alcohol, staying hydrated, and only having an alcoholic drink with or after food. 

If you feel like you’re dealing with hangovers often or are worried about your symptoms, chat your doctor (GP) or contact a support line.

  1. Department of Health, Victoria. How alcohol affects your body. 2020. Better Health Channel. Available from: https://www.betterhealth.vic.gov.au/health/healthyliving/how-alcohol-affects-your-body

Page last updated7 August 2023