How Much Water Should You Drink When Exercising? (UK 2026)

Hydration is one of those topics where the advice swings between two extremes. One week you are told to carry a two litre bottle everywhere, the next you read that thirst is all you ever need. The honest answer sits in the middle, and it is simpler than most of the noise suggests. This guide covers why hydration matters when you train, roughly how much to aim for across the day, what to do before, during and after a session, and the signs that tell you when you have got the balance wrong in either direction.

Why does hydration matter when you train?

Water does a lot of quiet work while you exercise. It helps carry blood and oxygen to the muscles you are using, keeps your joints moving smoothly, and lets you shed heat through sweat so you do not overheat. When you lose more fluid than you take on, your blood volume dips slightly and your heart has to work a little harder to do the same job. That is part of why a run or a HIIT session can feel unusually heavy on a hot day even when your legs are fresh.

Sports nutrition research generally suggests that once fluid losses climb past roughly two per cent of your bodyweight, exercise starts to feel harder and performance can dip, and the effect is larger in heat. For most everyday training the impact is modest rather than dramatic, so there is no need to panic about every drop of sweat. The practical takeaway is calmer than the headlines: turn up reasonably well hydrated, drink sensibly around your session, and top back up afterwards.

How much water should you drink in a day?

The NHS points to the Eatwell Guide figure of around 6 to 8 cups or glasses of fluid a day, which works out at roughly 1.2 to 2 litres, on top of the water you get from food. European food safety guidance frames it slightly differently, suggesting a total water intake of about 2 litres a day for women and 2.5 litres for men, counting fluid from both drinks and food. In practice food supplies a decent share of that total, so you do not need to drink the whole figure.

Treat these as starting points rather than strict targets. Your real needs shift with your body size, the weather, how much you sweat and how hard you are training. Someone doing two sweaty sessions in a warm week will need more than the same person resting on a mild day. Water is the obvious choice, but tea, coffee, lower-fat milk and sugar-free drinks all count towards the total, so hydration does not have to mean plain water alone.

How much should you drink before, during and after training?

You do not need a rigid schedule for a normal session, but a loose plan helps, especially for longer or hotter efforts. The aim is to start well hydrated without feeling waterlogged, drink to comfort during the session, then replace what you lost afterwards.

For most people, drinking to thirst during a session under about an hour in normal conditions is genuinely enough, and the science backs that up for everyday training. The picture changes when a session runs long, the weather is hot, or you are a heavy sweater, and that is when a steadier sip-as-you-go approach pays off. For long efforts, a simple after method is to weigh yourself before and after and drink back around one and a half times the weight you lost over the following few hours.

Can you drink too much water?

Yes, and it is worth taking seriously even though it is uncommon. Drinking far more plain water than you are losing, usually across very long events lasting several hours, can dilute the sodium in your blood. This is known as exercise-associated hyponatraemia, and in its serious form it can be dangerous rather than just uncomfortable. It tends to show up on ultra-distance races, long hot events and marathons, where some people drink at every opportunity out of fear of dehydration.

The reassuring part is that it is largely preventable. The widely recommended safeguard is to drink to thirst rather than forcing litres of plain water on a strict schedule, and to include some sodium through food or a suitable sports drink on very long, sweaty efforts. In short, more is not automatically better, and the goal is to match your drinking to your losses rather than to drown them.

How do you know if you are getting it right?

You do not need lab equipment to keep tabs on your hydration. Three simple checks cover most situations, and together they give you a decent read without any guesswork.

• Urine colour. Most people are aiming for a pale straw colour. Consistently dark urine suggests you could drink a bit more, while long stretches of completely clear urine on a big training day can be a sign you are overdoing plain water.
• Thirst. For everyday sessions, thirst is a reliable everyday guide. If you are thirsty, drink. If you are not, you usually do not need to force it.
• Bodyweight on long sessions. For longer efforts, a quick weigh-in before and after shows roughly how much fluid you lost, which you can then replace steadily rather than in one go.

If you feel light-headed, get a nagging headache, or your performance falls off a cliff, treat that as a prompt to check in rather than to guess. Those signs can point either way, towards too little or too much fluid, which is exactly why the simple checks above are so useful.

When do electrolytes and sports drinks actually help?

Electrolytes, mainly sodium, are lost in sweat, and replacing them matters most when you sweat a lot for a long time. For a short, easy session, plain water and a normal balanced diet cover it comfortably, so there is no need to reach for a coloured drink after a 30 minute jog. The case for electrolytes or a sports drink grows as sessions get longer, hotter and sweatier, roughly past the hour to ninety minute mark, or if you are a naturally salty, heavy sweater.

You do not need anything fancy to make this work. Category options such as electrolyte tablets, sachets or a standard sports drink all do a similar job, and on very long days some sodium from food helps too. The main thing is to match the tool to the session rather than defaulting to a sugary drink for every workout. Getting the basics right, water for most sessions and electrolytes for the big ones, covers the vast majority of members.

Hydration is really a habit, and habits are easiest when the training around them is clear. Edge is a training app rather than a drinks brand, so it will not sell you a bottle, but a plan that tells you how long and how hard each session is makes it much easier to judge when to sip water and when a session is big enough to warrant electrolytes. With 18,000+ members training across running, strength, HIIT and mobility, the goal is to make the sensible choice the obvious one.

This article is general guidance, not medical advice. If you are new to exercise, returning from injury, pregnant, or managing a health condition, speak to your GP before starting, and see a physio for any niggle that does not settle.