Dehydration and how to avoid it

Whether you’re exercising or not, it’s important to stay hydrated. Here’s our guide on why hydration is important, how much you need to drink and what should be in your bottle.

Why is hydration important?

More than half of your body is made up of water so it’s clear that controlling your water intake is essential. Water is important for many processes in your body. This includes transporting nutrients and oxygen around your body, regulating your temperature and getting rid of waste products.

On average, you gain and lose around two and a half litres of water a day, although this varies from person to person and when you exercise, this increases significantly, mainly through sweating and faster breathing. But before you think that hydration is only important during exercise, your brain is also heavily made up of water, and insufficient hydration can significantly affect your brain function. It's important to hydrate properly when cycling

What happens if you don't top up your fluids?

If you don’t replace the water you lose, you become dehydrated. Dehydration occurs when you lose more water than usual, such as through vomiting or diarrhoea, or when you simply haven’t drunk enough. Other causes for dehydration include increased sweating or drinking too much alcohol.

Being dehydrated can affect both your general health and how well you can exercise. You’ll feel tired more quickly and you won’t be able to control your temperature as well as usual. Research shows that losses of 2% or more can reduce your mental performance, which can include short-term memory, arithmetic efficiency, motor speed and attention. The more dehydrated you are, the bigger the effect.

So, how can you tell if you're dehydrated or not?

One of the best indicators is the number of times you need to go to the toilet and the colour of your urine, which should be pale yellow. If you don’t have to go as often as you normally would, and your urine is of a dark colour, it’s likely that you’re dehydrated. Having a headache, and feeling lethargic and tired can also be a sign of dehydration. During exercise, a dry mouth or lip can also be a strong indicator. Recognising early dehydration signs is crucial to taking timely action to rehydrate and prevent further health issues. Do you feel a headache after your run? You can learn the main causes of headaches after running here.

If you are dehydrated, then you need to rehydrate your body with fluids. It’s better to drink little and often rather than trying to drink a lot all in one go. A drink with electrolytes is also beneficial because dehydration can also change your electrolyte balance and decrease key minerals in your body. Electrolytes are minerals in your body that help your body’s blood chemistry, muscle action and process. Sodium, potassium, calcium and magnesium are all electrolytes. Ideally we should, of course, prevent dehydration in the first place so let’s have a look at what you can do to stop it happening! Rehydrate properly during and after sport

Throughout the day/ Before Exercise

The European Food Safety Authority (EFSA) recommends a daily intake of 2.5 litres of water for men and 2.0 litres of water for women. This should mainly come from drinks but a small proportion (around 20-30%) should also come from food. Fruit and vegetables are high in water. Thirst is your most obvious indicator of hydration status and drinking to quench thirst can be a good habit. Of course, urine colour as mentioned earlier is another useful hydration indicator. The darker it is, the more dehydrated you are. But beware that some foods, like beetroot, can also change the colour of your urine.

With HIGH5 ZERO it has never been so simple to stay hydrated throughout the day. Simply drop the effervescent tablet into water for a refreshing sugar free electrolyte drink with zero calories. The scientific formula also includes Vitamin C to support a healthy immune system, and reduce tiredness and fatigue. Most people don’t think much about pre-hydration, but making sure you are well hydrated before you exercise is really important, especially in warmer weather.

If you’re dehydrated before you even start exercising, you will make your heart work harder and your body will find it more difficult to control your core temperature. All this can lead to a drop in performance, and potentially be risky to your health too. Starting well-hydrated means you can enjoy your sport more.Rehydration station for runners at Bath Half marathon

During Exercise

Being dehydrated can affect your energy levels. Your muscle cells are almost three-quarters water so if you're short on fluids, you’ll feel the strain. Drinking little and often will give you the best chance of hitting your exercise targets. But what should you be drinking and how much? This largely depends on how much you sweat and how long you exercise for. Going by thirst can be good practise but there are many athletes’ that still don’t drink enough. Here is an easy way to calculate how much you sweat during exercise:

1. Weigh yourself before exercise.

2. Weigh yourself after exercise.

3. Calculate the difference of your pre and post exercise weight and add any fluids you consumed during this period too.

4. Divide the difference by the duration of exercise for your hourly sweat rate.

Here’s an online calculator that lets you easily calculate sweat rates based on the above steps. Now that you know how much you should be drinking, let’s have a look at what should be in your drinks bottle. The choice of sports drinks on the market can be overwhelming and you could be forgiven for not knowing which one to choose.

What type of sports drink you need during exercise, depends largely on the duration of exercise.

Up to 90 minutes: You have enough energy stored in your muscles to fuel your sport. Your main focus should be on hydration which can be achieved with a zero calorie electrolyte drink like HIGH5 ZERO.

Over 90 minutes: During endurance exercise, you need to focus on both hydration and energy to keep you going for longer. Carbohydrate-electrolyte solutions enhance the absorption of water and helps your endurance performance.

HIGH5 Energy Drink is a scientifically formulated carbohydrate and electrolyte sports drink designed for use during exercise to both replace key electrolytes and supply energy to your muscles. During exercise, athletes can be at risk from hyponatremia, also known as water intoxication, which is generally the result of drinking excessive amounts of plain water with no electrolytes during endurance events. This causes a low concentration of sodium in the blood. Some of the symptoms include muscle cramps, headache, feeling disorientated and vomiting.

For strategies on maintaining electrolyte balance and additional cramp prevention tips, explore our detailed guide to keep your training sessions smooth and uninterrupted.

Runner sat drinking from HIGH5 Bottle in a park

After Exercise

Even with a good hydration strategy, you often finish exercise mildly (or more severely in hot conditions) dehydrated, so it’s important to continue drinking after exercise. You should aim to replace 150% of your fluid lost through exercise within 3 hours of finishing. This means that if you finish exercising with a one litre fluid deficit, you should drink 1.5 litres. Not only will this be refreshing, but it will also restore your fluid levels. A drink that also contains carbohydrates and protein, like HIGH5 Recovery Drink, will also enhance your recovery and help grow your muscles.


ZERO is a refreshing sugar free electrolyte drink with zero calories that makes it simple and easy to stay hydrated. When you sweat, you lose vital minerals so it's important that they are replenished. With key electrolytes, sodium and magnesium, ZERO gives you what water can't. Get yours here.

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