A Runner's Guide to Hydration: How Much to Drink, What to Drink, and How to Carry It

This guide covers everything you need to know about hydrating as a runner, including what to drink day-to-day; how electrolytes work; how much water to drink before, during, and after training; and how to carry water on your long runs.

Like our running nutrition guide, the advice here is what works for most runners most of the time. Once you understand the basics, listen to your body and focus on what works for you.

Everyday hydration for runners

Most of us go about our lives without giving too much thought to hydration. We drink when we're thirsty, and that's good enough. But if you’re training regularly, your body loses more fluid than it otherwise would, and if you don’t replace it, you’re starting on the back foot.

A sensible approach is to keep a water bottle with you and drink small amounts throughout the day, rather than tanking up all in one go. And on the days you train, you'll probably need a bit more than usual.

Because hydration is so individual, the best guideline available is the colour of your pee. Pale yellow is the ideal. If it's darker than that, you need to drink more; if it's lighter, you could probably drink a bit less without any problems.

Some things to bear in mind:

• Caffeine isn't the enemy. Yes, it can dehydrate you slightly when you drink a lot of it, but one or two cups of coffee iwon't have a meaningful impact, and it can even help you perform better on your runs.
• Alcohol will impact your runs. Drinking alcohol will dehydrate you, and the effects last longer than you might think, sometimes up to 48 hours. I'm not saying don't drink, but expect your runs to feel harder afterwards.
  
• Food counts towards your fluid intake. Soup, fruits, vegetables, and yoghurt contribute to your daily intake.

Common signs of dehydration include headaches, poor sleep, fatigue, a dry mouth, and runs that feel much harder than they should. Fortunately, the fix is pretty simple: keep a water bottle nearby and fill it up throughout the day.

Do you need electrolytes?

Electrolytes have surged in popularity recently. A few years ago, you'd have had to go to a specialist sports shop to find them; now they occupy a large section of the supplements aisle in most supermarkets, and you'll see influencers stirring sachets into their bottles for anything from morning workouts to hangovers and the school run. The message is that you basically can't function well without them.

Most of that is absolute nonsense.

Electrolytes are minerals, such as sodium and potassium, that support different processes in your body. They regulate fluid balance, make your muscles contract, and power your nervous system.

You lose these minerals when you sweat, and if you don't replace them, you can end up with cramps and headaches. In extreme situations, you might even end up with hyponatraemia (more on that later).

Your body is generally pretty good at managing its own electrolyte balance, despite what influencers will tell you. For most people, a balanced diet will top up the minerals you need without any extra assistance.

The picture is slightly different for runners because you’re losing more through sweat than the average person, especially if you exercise when it’s hot outside. That doesn’t mean you need to be knocking back an electrolyte sachet every morning, though. It means you need to consider situations in which they might actually help.

When you don't need electrolytes

• For any run under an hour

• On a normal day when you’re not training

When you might need electrolytes

• For runs over 60 minutes

• After a hot, hard race

Salt tablets vs electrolyte tablets/sachets vs sports drinks

These products mostly do the same job in slightly different ways.

• Electrolyte tablets/sachets dissolve in water, giving you a flavoured drink with a balanced mix of minerals. They’re an easy option for most runners and work well for long training runs and races. I like the mixed berry flavour of Phizz electrolytes because it’s not too sweet.

• Salt tablets are small capsules you swallow with water. They’re more concentrated, so they're popular with ultra runners and people who sweat heavily. If you lose a lot of salt when running (your skin is crusty with it after a long run), these might be for you.

• Sports drinks like Lucozade combine carbs with electrolytes, so they double as a source of fuel. They’re handy for races where you’d be taking gels anyway, but be careful not to overdo it if you’re drinking plain water too.

As with most things, the right option comes down to personal preference, what your stomach can handle, and what's easiest to carry.

Timing your electrolytes

If your run will be longer than two hours, start taking electrolytes in the 24 hours before it to help your body prepare. During the run, aim for 700-900mg electrolytes per litre of fluid, and sip regularly, rather than waiting until you feel like you need them. It's better to stay ahead of the game instead of trying to fix a deficit halfway through.

What to drink before a run

Consistency is the key to getting your hydration right. If you regularly sip water throughout the day, a single glass of water 30-60 minutes before you set off will do the job nicely. If it's a longer run (60+ minutes), or the weather is hot, you will probably need a bit more. The important thing is making sure you give yourself time to absorb whatever you drink; otherwise, it will slosh around while you're running, which is deeply unpleasant.

Early morning runs

Early runs are a bit trickier to hydrate for, because your body loses water through your breath while you sleep, so you might wake up a bit dehydrated. Drink a glass of water as soon as you wake up, and by the time you head out of the door, you should be good to go. If you're planning on doing a long run, it's worth adding a sachet of electrolytes to your morning drink and taking something with you to sip on while you run.

The golden rule

Never try anything new before a race. The same goes for fuelling and pretty much everything else. Race morning is not the time to experiment; stick to what you know.

Hydrating during a run

How much you need to drink during a run depends on how far you're going, how hot it is, how much you sweat, and how hard you're working.

• Under an hour: You probably don’t need to drink anything at all unless it’s especially hot.

• One to two hours: Aim for around 400-800ml, sipped steadily across the run.

• Over two hours: Aim for 500-800ml per hour (more when it’s hot; less when it’s cool).

These numbers are just ballpark estimates; every runner is different, so it's worth experimenting during training runs to find out what works best for you. Some runners prefer to drink only when they feel thirsty, but on longer runs, it's a good idea to have a hydration plan to stay ahead of that thirst - by the time you feel it, it's probably already having an impact on your running performance.

Don't overdo it

Drinking too much during heavy exercise (especially on a longer run) can lead to hyponatraemia, a condition where the sodium in your blood becomes dangerously diluted. The people most at risk are slower runners who stop at every water station and drink lots between them when they don't need to.

How to carry water on a run

When your runs last longer than an hour, you need to think about how to take water with you. There are loads of great options out there that minimise the inconvenience.

Handheld bottle

A purpose-built running bottle or soft flask you hold in your hand. Many are ergonomically designed or come with a strap, so you don’t have to grip it for the whole run.

• Good for: runs up to 90 minutes, races where you want your own drink rather than relying on water stations.
• The downsides: holding a bottle while you run can be a bit annoying, especially when your grip gets sweaty and you feel tired.

Running belt

A small, lightweight belt that sits around your waist with a couple of small bottles clipped in, plus a few pockets.

• Good for: medium-length runs (60-120 minutes) where you want your hands free but don’t want to carry loads.
• Downsides: small bottles mean you might run out of water on longer runs, and cheaper belts can bounce around, which is incredibly annoying.

Hydration vest

A lightweight vest that sits close to your body with soft flasks in the front pockets and often a bladder in the back.

• Good for: long runs (over two hours), trail running, ultras, and any race where there might not be regular water stations.
• Downsides: overkill for shorter runs; can chafe if you don’t get one that fits well, especially on long hot runs.

Bladder pack

Similar to a vest, with a large bladder in a small backpack that you drink through a tube over your shoulder.

• Good for: long trail runs, ultras, hiking-style runs.
• Downsides: they can be difficult to clean, and the drinking tube can start to taste a bit gross after a while. The extra weight also sits higher on your back than a vest, which is uncomfortable for some runners.

Hydration during race week and race day

Now is the time to stick to what you know works, with a few small adjustments as you approach race day.

The week before

Drink water as you normally would, sipping throughout the day. More water doesn't necessarily equal better hydration, so resist the temptation to drink loads more - it can actually make your body flush out fluid faster, leaving you more dehydrated at the start line than you would have been with a more consistent approach.

The day before

Sip water throughout the day, and avoid chugging loads in the evening. The aim is to be well hydrated by bedtime; you don’t want your sleep disrupted by needing to use the toilet in the middle of the night. Avoid alcohol and keep your caffeine intake at the usual level. If it's going to be a long, hot race, you might want to take some electrolytes.

Race morning

Have a glass of water when you first get up, then sip steadily as you get ready. Again, chugging water at this point is a bad idea; you don’t want to be sloshing at the start line, and the pre-race portaloo queue is something you want to avoid if at all possible.

During the race

Should you stop at water stations?

If you're running a shorter race (5k or 10k) and you're properly hydrated, the answer is probably no. For longer races, treat water stations like a chance to top up rather than a full stop. Ideally, carry water with you so you don't have to stop at all.

Should you drink water or a sports drink?

If you're using gels, water is usually the better option. If you're not carrying fuel, a sports drink will hydrate you and give you a little extra energy, which is a win-win.

How to time hydration with fuel

Drink water at the same time as your gels to prevent stomach upsets. Most importantly, stick to whatever works well from your training sessions.

Adjust for the weather

Hot weather makes you sweat more, so drinking plenty becomes even more important. You'll probably need more than you think. On cold days, you can drink less, but hydration is still important.

Post-run and post-race recovery

It's easy to get swept up in the awesome post-race atmosphere after you cross the finish line and forget to eat or drink, but the next hour is an important window for rehydration. Drinking water alone is fine after a short run. If you were out for longer than an hour or you sweated a lot, you might want to have a salty snack like a pretzel alongside your water, drink a sports drink instead, or add some electrolytes. Chocolate milk is also a popular recovery drink because it contains the perfect ratio of carbs to protein.

After a marathon or ultra, recovery takes a lot longer. Keep on top of your hydration in the following days by drinking plenty and eating well too.

A few final notes

Everyone's different. What works well for one runner won't necessarily work for you. Use this guide as a starting point, then listen to what your body tells you and adapt.

Hydration is one piece of the puzzle. While staying hydrated will help you perform at your best, it isn't the only thing that matters, and it can't work miracles on its own. Think of it as an important part of your day-to-day routine as a runner, not as a magic fix.