You don't need to be a scientist to see the toilet queues on a Saturday night, or at an event, to make the link between drinking alcohol and the need to pee. So why exactly does drinking alcohol make us need to pee more than when we drink soft drinks or water?
“Alcohol is a diuretic,” says Professor Oliver James, Head of Clinical Medical Sciences at Newcastle University. “It acts on the kidneys to make you pee out much more than you take in – which is why you need to go to the toilet so often when you drink.” In fact for every 1g of alcohol drunk, urine excretion increases by 10ml1.
Alcohol also reduces the production of a hormone called vasopressin, which tells your kidneys to reabsorb water rather than flush it out through the bladder. With the body's natural signal switched off, the bladder is free to fill up with fluid.
A common side effect of drinking is needing the toilet just five minutes after your last visit. This irritating experience (usually known as 'breaking the seal') happens because alcohol delivers a hefty double whammy to your kidneys.
"Suppose you have a pint at lunchtime," explains Oliver. "At some point you'll need to go to the toilet and get rid of the pint of liquid you've just drunk. Then, an hour later, you'll have to pee again because of the added diuretic effect."
Switching to alcoholic drinks with less volume, such as shots, won't stem the flow either. That’s because whether you're drinking pints or doing shots, it's the diuretic element of the alcohol which is key to producing all that wee.
Unfortunately not. Because alcohol promotes peeing, it can lead to dehydration, which causes the nausea and headache associated with bad hangovers. It's also why your mouth might feel like the driest place on earth the next day.
With fluid leaving your body so quickly, dehydration can be a big problem. Though it might seem like even more liquid is the last thing you need when you’re having to dash to the gents/ladies, regular sips of water during and after drinking are what you need to keep yourself hydrated.
(1) Eggleton MG, ‘The diuretic action of alcohol in man’,J Physiol 1942, vol.101, pp.172-191. Available at: