A group of friends, drinking and laughing together.

What causes a hangover?

You already know the short answer to this – alcohol.

Or to be more specific, a substance found in alcohol called ethanol.

In addition to providing the buzz of choice for humankind for thousands of years, ethanol is also a toxic chemical which among other uses, is used as an industrial solvent added to gasoline for vehicle fuel. 1

So, it’s no surprise that ethanol is responsible for some nasty effects in the human body.

These include: 2 , 3

  • Dehydration - ethanol is a diuretic, meaning it causes you to lose water through frequent urination. Drinking alcohol also makes you sweat, causing you to lose even more water. This causes thirst, a dry mouth, weakness and dizziness.

  • Upset stomach – your stomach acid production increases, irritating your stomach lining. This can lead to bloating, diarrhoea and vomiting.

  • Disrupted sleep – you may have been out cold for eight hours or more, but drunk sleep is of low quality and unlikely to leave you rested. Having a hangover causes emotional symptoms too, such as sadness and anxiety which are exacerbated by lack of sleep.

  • Alcohol withdrawal –when you stop drinking, your nervous system (responsible for movement and balance) goes into overdrive. This is what causes the shakes, dizziness and rapid heartbeat.

  • Electrolyte imbalance – the loss of fluids associated with drinking alcohol (caused by vomiting, sweating and frequent urination) causes you to lose valuable electrolytes. These mineral compounds are responsible for energy production and explain that fatigued, weak feeling.

What causes the headache of a hangover?

One of the most common signs of a hangover, the pounding head, is caused by a mixture of dehydration, lack of sleep and expanding blood vessels in the brain, stimulating pain receptors. 4

Hangover symptoms

  • Fatigue
  • Headache
  • Sensitivity to light and sound
  • Red eyes
  • Dry mouth
  • Muscle aches
  • Thirst
  • Rapid heartbeat
  • Sweating
  • Dizziness
  • Anxiety
  • Depression
  • Nausea and vomiting
  • Body chills

How do you stop a hangover? 


You don’t need us to tell you the most obvious way to stop a hangover – and that’s to not drink in the first place.

Read more: Dry January: The benefits of being alcohol-free

In terms of prevention, there are a few things you can do to lessen the severity of the hangover you do get. These include:

  • Hydrate – if you’re already dehydrated, alcohol will wreak extra havoc on your depleted body. Drink at least 6 – 8 glasses of water (1.2 litres) 5 throughout the day if you know you’re going to be drinking alcohol that evening.

  • Eat – you need to ensure you have something in your stomach before that first drink hits. By ensuring alcohol stays in the stomach longer, having a meal beforehand will slow the rate at which alcohol is absorbed by the small intestine and into the bloodstream, meaning you get drunk slower. 6

  • Hydrate again – while you’re drinking, it’s crucial to drink a few glasses of plain water or a non-alcoholic option alongside your alcoholic beverages. This means that for every loo break you have, your body will have a ready supply of water to rehydrate it instead of something alcoholic.

  • Plan - if you are serious about wanting to lessen a hangover, you need to do some planning. Whether that’s finding a table near the toilets (for all those loo breaks that come with better hydration), or agreeing with a non-drinking friend to enforce the 1 drink = 1 water rule when your own resolve starts to slip. Make it a rule to always order two drinks at a time – as long as one of them is water, and not order another until both drinks are finished.

  • Hydrate yet again – have a large glass of water when you get in from drinking. Keep a large bottle (a glass might get spilled if you’re a little clumsy) of water on the bedside table and take sips if you wake during the night. You’ll need to go to the toilet more, but it’s worth it for extra hydration.

How long does a hangover last?


A hangover usually begins a few hours after the drinking stops. This is when your blood alcohol level starts to fall and the buzz wears off.

Hangover symptoms usually peak about the time the alcohol leaves the system (when the blood alcohol level is zero) and may continue for up to 24 hours thereafter. 7

Can you cure a hangover by drinking more? 


As hangover symptoms peak around the time your blood alcohol level reaches zero, you can technically delay the inevitable by having another alcoholic beverage and bumping your blood alcohol level up slightly for a few more hours.

However, this is a very bad idea. You can’t escape a hangover, and by adding more alcohol to your body you’re simply guaranteeing that your hangover symptoms – when they do arrive slightly later – are even worse.

Drinking to ‘help’ a hangover when done frequently is a major risk factor for alcoholism. 8 Speak to your GP if you or a loved one is concerned about your drinking. Shop Low Alcohol & Alcohol Free Drinks

Last Updated: 25th November 2020

bhupesh-panchal2

Author: Bhupesh Panchal, Regulatory Affairs

  • Joined Holland & Barrett: April 2019
  • Qualifications: Masters Degree in Toxicology, BSc Hons in Medical Biochemistry

Bhupesh started his career as a clinical toxicologist for Public Health England, advising healthcare professionals all around the country on how to manage clinical cases of adverse exposure to supplements, pharmaceuticals, cosmetics, industrial chemicals and agricultural products. After 7 years in this role and a further year working as a drug safety officer in the pharmaceutical industry, Bhupesh joined Holland & Barrett as a Senior Regulatory Affairs Associate in 2019.

Bhupesh specialises in vitamins & minerals nutrition, health benefits & safety of botanicals and traditional herbal medicines. View Bhupesh's LinkedIn profile. In his spare time, Bhupesh likes to cycle and has been learning to speak Korean for several years.
AlcoholAlternative Health