Back to top
Menu
Keeping hydrated for exercise
Expert reviewer, Dr Leon Creaney, Sports & Exercise Medicine Consultant
Next review due March 2021
Whether you’re an elite athlete or a weekend warrior, hydration is key during exercise.
Here are some of our top tips to help guide you on how much you need to drink, and what to drink, before, during and after exercise.
Why is hydration important during exercise?
Around 60 per cent of your body is water and it plays a vital role in every bodily function. You can lose a lot of fluid when you exercise – as much as a litre or two an hour – mainly through sweating and breathing.
If you don’t top this fluid back up, you can get dehydrated. This can affect both your general health and how well you can exercise. You’ll feel tired more quickly if you’re dehydrated, and you won’t be able to control your temperature as well as usual.
Water helps fuel your muscles, so drinking before, during and after exercise will boost your energy levels, and may help to prevent cramp.
Hydration before you exercise
It may not cross your mind, but making sure you’re well hydrated before you exercise is really important, especially in hot conditions.
If you’re dehydrated before you start exercising:
- your core temperature will rise faster
- your heart will have to work harder than usual
This will affect your performance and can even lead to heat stroke. Drinking enough will help you get the most out of your exercise session and feel good while you’re doing it.
One quick way to test if you’re hydrated is to check the colour of your urine.
Top tip
It can take time for fluids to be absorbed into your body. So drink steadily during the day and aim to drink around 500ml of fluid at least four hours before you exercise. In the 10 to 15 minutes before you exercise, top up your fluid levels by drinking about half this amount again.
Hydration during exercise
It’s important to drink water during a workout – take a water bottle with you on a run, for example. Being dehydrated can affect your energy levels. Your muscle cells are almost three-quarters water so if you're short on fluid, you’ll feel the strain. Drinking little and often rather than a lot less often will give you the best chance of hitting your exercise targets.
How much you need to drink will depend on how much you sweat and how long you exercise for. How much you sweat and lose water is influenced by your:
- size – larger people tend to sweat more than smaller people, and men sweat more than women
- fitness – fitter people sweat more and earlier in exercise because their bodies are accustomed to needing to cool down
- environment – you sweat more in hot, humid conditions
- exercise intensity – you sweat more as you exercise harder
The best way to figure out how much to drink is to respond to what your body tells you. If you feel thirsty, you really need to drink as your body is already showing signs that it needs to take on more fluid. Here’s another way to work out how much fluid you lose while exercising and how much to drink to compensate for it.
The sweat rate calculation
Weigh yourself before exercise (ideally do this first thing in the morning after you go to the toilet).
Weigh yourself after exercise.
Compare the figures.
For every kilogram of body weight you lose, drink up to a litre and a half of fluid.
Top tip
Make sure you always have a bottle of water handy when you exercise so you don’t get dehydrated.
Smarter living. It’s in your DNA. Bupa SmartDNA examines your genetic composition to help you eat, move and think smarter. You’ll get help from a health and wellbeing coach to make sense of the science, and build a plan around your body, so that you have the tools you need to live smart. Learn more about SmartDNA >
Smarter living. It’s in your DNA.Hydration after exercise
Once all the hard work is over, no doubt you’ll be ready for something to drink. Not only will this be refreshing, but it will also restore your fluid levels and help your muscles to recover. The sooner you start to replace the fluid, the sooner you’ll recover.
Top tip
Don’t be tempted to reward yourself after exercise with a pint or a glass of wine. Alcohol is a diuretic, which means it removes water from your body by increasing how much urine your kidneys produce.
Do I need to drink sports drinks?
The array of sports drinks on the market can be overwhelming and they can contain lots of added sugar. So it’s hard to know which to choose and if they really offer any benefit.
If you’re doing moderate amounts of exercise, you won’t need them. Simple water is often the best thing to drink during and after a workout. But if you’re doing strenuous training, sports drinks may be useful.
- If you’re exercising for less than an hour, water is all you need to keep hydrated.
- If you’re exercising for longer than an hour, sports drinks or even just squash can help you keep going for longer. As well as replacing lost fluid, they contain carbohydrates (sugar) and electrolytes like sodium, potassium and magnesium, which you lose though sweat. These drinks provide fuel and help to keep you hydrated.
Make your own sports drink
To avoid spending lots of money on sports drinks which may contain lots of sugar and additives, try making your own at home. Mix 200ml squash (not a low-sugar variety) with 800ml water and add a large pinch of salt.
If you’re training for an endurance event like a marathon or triathlon, speak to a dietitian for advice that’s personalised for you. For more information, take a look at our guide on nutrition for sports and exercise.
Can you drink too much?
Drinking too much can potentially be harmful as it can cause a rare condition called hyponatraemia. This is when you drink more fluid than you lose through sweating and weeing. The excess water dilutes the salts in your body and your cells swell up, which can cause a number of problems. The amount you have to drink to get hyponatraemia varies hugely from person to person. The symptoms include:
- feeling confused or disorientated
- difficulty balancing
- a headache
- feeling sick or vomiting
- feeling bloated
In a worst-case scenario, severe hyponatraemia can lead to a coma, seizures (fits) and even death.
If you have any of the symptoms above while you’re drinking while exercising, seek urgent medical advice.
Top tip
Get to know what your sweat rate is (see our Hydration during exercise section above) and track how much you’re drinking. If you’re using a refillable bottle, make a mental note of how many times you top it up.
About our health information
At Bupa we produce a wealth of free health information for you and your family. We believe that trustworthy information is essential in helping you make better decisions about your health and care. That’s why our content is produced to the highest quality standards. Look out for the quality marks on our pages below. You can find out more about these organisations and their standards on The Information Standard and HON Code websites.
 |
 |
|---|
Tools and calculators
Physical activity quiz
How much physical activity should you be doing? Take our physical activity quiz and test your knowledge about the importance of staying active.
Healthy eating quiz
A healthy balanced diet is essential for your physical and mental wellbeing. Take our healthy eating quiz to find out how much you know about nutrition.
-
Sources
- Sports nutrition. American Academy of Orthopaedic Surgeons. orthoinfo.aaos.org, last reviewed December 2014
- Water and sodium balance. The MSD Manuals. www.msdmanuals.com, last full review/revision November 2016
- Renal symptoms during exercise. Brukner & Khan's clinical sports medicine (online). 4th ed. MH Medical. csm.mhmedical.com, published 2012
- Dehydration. Medscape. emedicine.medscape.com, updated December 2017
- Muscle cramps. The MSD Manuals. www.msdmanuals.com, last full review/revision July 2016
- Fluid. British Dietetic Association. www.bda.uk.com, published March 2017
- Dehydration. Medscape. emedicine.medscape.com, updated 31 December 2017
- Selecting and effectively using hydration for fitness. American College of Sports Medicine. www.acsm.org, published 2011
- Healthy hydration guide. British Nutrition Foundation. www.nutrition.org.uk, revised January 2016
- Sport. British Dietetic Association. www.bda.uk.com, published April 2017
- Hydrate right during physical activity. Academy of Nutrition and Dietetics. www.eatright.org, published 23 March 2015
- Electrolytes and fluid balance. Oxford handbook of nutrition and dietetics. Oxford Medicine Online. oxfordmedicine.com, published January 2012
- European Food Safety Authority. Scientific opinion on dietary reference values for water. EFSA Journal 2010; 8(3):1459. doi:10.2903/j.efsa.2010
- Fluids for athletes. Coaching Association of Canada. www.coach.ca, accessed 11 January 2018
- Selecting and effectively using sports drinks, carbohydrate gels and energy bars. American College of Sports Medicine. www.acsm.org, accessed 10 January 2018
- Hyponatraemia. BMJ Best Practice. bestpractice.bmj.com, last updated 2 November 2017
- Hew-Butler T, Ayus JC, Kipps C, et al. Statement of the second international exercise-associated hyponatremia consensus development conference, New Zealand, 2007. Clin J Sport Med 2008; 18(2):111–21. doi:10.1097/JSM.0b013e318168ff31
-
Author information
Reviewed by Rachael Mayfield-Blake, Freelance Health Editor, March 2018
Expert reviewer, Dr Leon Creaney, Sports & Exercise Medicine Consultant
Next review due March 2021
Has our health information helped you?
We’d love to know what you think about what you’ve just been reading and looking at – we’ll use it to improve our information. If you’d like to give us some feedback, our short survey will take just a few minutes to complete. And if there's a question you want to ask that hasn't been answered here, please submit it to us. Although we can't respond to specific questions directly, we’ll aim to include the answer to it when we next review this topic.
Legal disclaimer
This information was published by Bupa's Health Content Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition.
The information contained on this page and in any third party websites referred to on this page is not intended nor implied to be a substitute for professional medical advice nor is it intended to be for medical diagnosis or treatment. Third party websites are not owned or controlled by Bupa and any individual may be able to access and post messages on them. Bupa is not responsible for the content or availability of these third party websites. We do not accept advertising on this page.
For more details on how we produce our content and its sources, visit the 'About our health information' section.
^We may record or monitor our calls
