Electrolytes vs water: What actually helps the next day?

We’ve all got a go-to remedy for the morning after a big night out. A salty bag of crisps. A cheesy pizza. A strong coffee with a dash of hope.

And somewhere near the top of most people’s list is a pint of water — or, increasingly, a fizzing electrolyte tablet dropped into one.

The logic feels obvious: alcohol makes you wee, weeing dries you out, dehydration gives you the hangover, so rehydrating fixes it. Except the research doesn’t quite say that. Alcohol is a diuretic, but the effect is smaller and shorter than the folklore suggests, and the studies that have measured it found that how dehydrated people were didn’t predict how rough they felt.

So does that make water and electrolytes pointless? No — but it does change what they’re for. Here’s what the evidence actually says about electrolytes vs water the morning after, and how to use both sensibly.

What are electrolytes?

Electrolytes are minerals that carry an electrical charge when dissolved in water. They help regulate some of the body’s most basic processes, including fluid balance, nerve signalling and muscle function.

The common ones are:

• Sodium
• Potassium
• Magnesium
• Calcium
• Chloride
• Bicarbonate
• Phosphate.

Together they set the balance of fluid inside and outside your cells. Sodium in particular is what decides whether the water you drink stays in your body or heads straight for the loo.

You get electrolytes from food and drink as part of a normal diet, and you can top them up with electrolyte tablets, powders, sachets or ready-made drinks.

Does alcohol actually dehydrate you?

A bit, yes. Alcohol suppresses vasopressin, the hormone that tells your kidneys to hold on to water, so you produce more urine than the drink alone would explain. That’s why you end up in the queue for the toilets on a night out. Scientists have known this since the 1940s, when the physiologist M. Grace Eggleton measured it in volunteers.^[1][2]

But the size of the effect is easy to overstate. In a 2017 randomised crossover trial, a moderate dose of alcohol (30 g, roughly three to four UK units) taken as wine or spirits increased urine output over the first four hours — but there was no difference at all once 24-hour urine was measured, and beer produced no more urine than alcohol-free beer at any point.^[4] In an earlier study, a litre of 4% beer produced only around 160 ml more urine over four hours than the alcohol-free version, and the diuretic effect was blunted in volunteers who were already dehydrated.^[3]

Put it together and you get a modest, short-lived effect. Drink heavily, skip water and sleep for seven hours, and you’ll wake up thirsty with a mouth like sandpaper. That part is real. It’s just not the whole story.

Does drinking alcohol affect electrolyte levels?

Less than you’d think. Alcohol’s diuresis is mostly a water diuresis: in the 2017 trial, the urine sodium and potassium findings simply mirrored the urine-volume findings — a small, short effect for wine and spirits, and none for beer.^[4] More importantly, when researchers measured electrolytes in people with a hangover, the levels didn’t correlate with how bad the hangover was.^[5] The idea that a night out leaves you dangerously “depleted” of sodium and potassium isn’t supported by the evidence.

Is dehydration what causes the hangover?

This is the bit most hangover advice gets wrong, so it’s worth being straight about it.

A widely cited 2000 review in the Annals of Internal Medicine listed dehydration among the likely causes of a hangover, alongside hormonal changes, immune-system activity and the toxic effects of alcohol itself.^[2] Since then the evidence has moved on. A 2010 review of studies that took blood and urine samples from hungover volunteers found that dehydration markers, including vasopressin, weren’t related to hangover severity — and neither were electrolytes, glucose, cortisol or a long list of other measures. The most convincing relationship was with immune factors.^[5]

Sleep matters too. In a survey of 578 students, people who slept less than seven hours after drinking reported more severe hangovers than those who slept longer.^[6]

So the honest summary is this: the thirst, dry mouth and slightly foggy feeling you wake up with are partly dehydration, and fluids fix those. The headache, nausea, exhaustion and general sense of regret are mostly the alcohol itself, the inflammatory response it triggers and the lousy sleep you’ve had — and no amount of water reverses that. Rehydrating is worth doing. It just isn’t a cure, and nothing in a bottle is.

Are electrolytes good for hangovers?

They can be a sensible part of your morning after, as long as you set realistic expectations.

Electrolytes aren’t a hangover cure, they don’t speed up the breakdown of alcohol, and they won’t do anything about the inflammatory side of things. What they do is make rehydration work better.

What do electrolytes actually do the morning after?

The useful one here is sodium. When you drink plain water after losing fluid, a lot of it passes straight through: the water dilutes your blood, your kidneys read that as “too much fluid” and switch urine production back on. Add sodium and your body retains more of what you drank. In a classic rehydration study, volunteers who drank a higher-sodium solution kept significantly more of the fluid than those who drank a low-sodium one, even when the volumes were identical.^[7]

That study used exercise to dehydrate people rather than alcohol, so read across with care — but the plumbing is the same. Sodium helps water stay put.

The other electrolytes have well-established roles you’re allowed to say out loud. Magnesium, for example, contributes to electrolyte balance, to normal muscle function and to a reduction of tiredness and fatigue — all wording taken from the GB register of authorised health claims. None of that is a hangover claim; it’s just what these minerals do in a normal diet.

What can’t electrolytes do?

Quite a lot, unfortunately. There are some things only time (and a nap) sort out. Electrolytes cannot:

• Speed up alcohol metabolism in the liver
• Reverse poor sleep caused by alcohol
• Settle nausea caused by stomach irritation
• Reduce alcohol-related anxiety (sometimes called hangxiety)
• Switch off the immune response that seems to drive most of the misery.^[5]

Does water help with a hangover?

It helps with the parts of a hangover that are dehydration: thirst, dry mouth and the sluggish feeling that comes with going eight hours without a drink of anything. It doesn’t cure a hangover, because dehydration isn’t what’s causing most of it.^[5]

Many people find it worth drinking water:

• During the evening, between alcoholic drinks (this mainly helps by slowing you down)
• Before going to sleep after a night out
• Steadily through the following morning, rather than in one enormous gulp.

What about coffee, tea and fizzy drinks?

Here’s a myth worth retiring: coffee does not dehydrate you. A 2014 crossover trial in 50 habitual coffee drinkers found no difference in total body water, urine volume or the standard blood and urine hydration markers between three days of moderate coffee and three days of the same volume of water.^[8] A meta-analysis of 16 studies put caffeine’s diuretic effect at around 100 ml of extra urine — minor, and negated entirely by exercise.^[9] The NHS counts tea and coffee towards your six to eight glasses of fluid a day.^[10]

So if your morning coffee is what gets you upright, have it. Just keep total caffeine sensible: the maximum recommended intake is 400 mg a day from all sources.

Sugary drinks and fruit juice hydrate you perfectly well too. The NHS advice is simply not to have high-sugar drinks too often, because of the calories and your teeth — not because sugar makes a hangover worse. There’s no evidence it does; we’ve gone through the research on that in our guide to low-sugar hangover recovery.

How much water do you need to drink to prevent a hangover?

Realistically, no amount of water will prevent a hangover. Hangovers are caused by the alcohol itself, the immune response it triggers and the sleep you didn’t get.^[5][6] Water addresses the thirst on top, not the hangover underneath. The only reliable way to reduce the risk is to drink less.

How to use electrolytes the morning after

If you want to use electrolytes after drinking, keep it simple:

• Drink to thirst, steadily. Sipping over an hour or two retains more fluid than downing a litre and then spending the morning in the bathroom.
• Get some sodium in. An electrolyte sachet, tablet or drink that actually contains sodium — check the label — or a salty breakfast alongside plain water.^[7]
• Eat something. Food brings its own salt and slows everything down, which helps the fluid stay where you put it.
• Then rest. Sleep debt is a bigger driver of how you feel than fluid debt.^[6]

Plenty of everyday foods bring electrolytes with them too: bananas and avocados (potassium), leafy greens (magnesium), yoghurt (calcium and potassium) and coconut water (potassium, with a little sodium).

Should you take electrolytes before or after drinking?

Either works; neither is magic. Some people take an electrolyte drink before bed after a night out, others reach for one the next morning. Bedtime probably makes the most sense — it’s the longest stretch you’ll go without fluids — but a drink taken before you start drinking won’t stop alcohol doing what alcohol does.

Can you drink electrolytes for hangover prevention?

No. Electrolytes can’t prevent a hangover, because dehydration isn’t what causes it.^[5] The only thing that reliably prevents a hangover is drinking less. What electrolytes can do is make the water you drink the next day count for more.

Electrolytes vs water for hangovers: a comparison

Both restore fluid. The difference is how much of it you keep, and what else comes with it.

Feel human again

Rehydrating is a sensible first move the morning after, and electrolytes make it work better. But as the research above shows, a hangover is more than a fluid problem — which is why a glass of water on its own rarely feels like enough.