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From park runs to gym sessions, staying hydrated matters. We ask an expert when to use electrolytes, if you need them more in hot weather and when water alone will do the job
Summary
1What are electrolytes?
Electrolytes are salts and minerals that carry an electrical charge and help regulate fluid balance and muscle function.
2Electrolyte benefits for exercise
Electrolytes help maintain hydration and may support endurance during longer or more intense exercise.
3When is the best time to use electrolytes?
During exercise, the body loses electrolytes, especially sodium, through sweat.
Do you really need electrolytes every time you exercise – or is water enough? Getting to grips with what electrolytes do for your body, their benefits and when to use them can make it easier to stay hydrated and support your performance.
As temperatures rise and outdoor training picks up, understanding hydration in hot weather UK conditions becomes even more important. “Water is usually enough for staying hydrated when doing low-intensity or moderate exercise like yoga or a short high incline walk, but for longer or more intense exercise like endurance sports or a park run, that’s where electrolytes can be more useful,” explains H&B Science Expert Heeral Tomlinson, who specialises in biomedical science.
There’s lots to learn, including what electrolytes are, their benefits, the best time to use them and how to spot dehydration. In fact, being dehydrated by as little as 2% of your body weight can impact exercise performance1,2 – which could be as little as a couple of water bottles’ worth of fluid lost through sweat.
We’ve also covered how hydration can affect your workouts and whether it’s possible to drink too much. So, on your marks, get set and let’s go...
What are electrolytes?
Electrolytes are minerals that help keep your body hydrated and functioning properly, especially when you are active. They play a key role in balancing fluids, supporting muscle function and keeping your nerves working as they should.3
“When we sweat, we don’t only lose water but also electrolytes, particularly sodium,” explains Heeral. As well as sodium, key electrolytes include:
- potassium
- chloride
- magnesium
- calcium
- phosphate
- bicarbonate
You get electrolytes through everyday foods and drinks but you can also top them up with supplements when needed.4
“For exercise over an hour, drinks containing some sodium and carbohydrate may help replace fluids”
Electrolyte benefits for exercise
Carbohydrate electrolyte beverages should be considered during prolonged exercise lasting longer than 90 minutes, to potentially support endurance performance.5
“For exercise lasting longer than around an hour, drinks containing some sodium and carbohydrate may help replace fluids lost through sweat and support performance,” says Heeral. Most of the time, electrolytes can be replaced through the food and fluids you consume daily. However, during longer or more intense sessions, especially where sweat losses are higher, replacing both fluids and electrolytes becomes more important.5,6
When is the best time to use electrolytes?
“Hydration needs increase when the weather is hot or when physical activity levels rise, so it’s important to drink before, during and after exercise to replace fluids lost through sweat,” explains Heeral.6
If you’ve just completed a shorter or lower-intensity session, this can usually be managed through normal eating and drinking.6 However, for longer workouts or endurance activity, electrolyte intake may become more beneficial.5
“A simple rule is that water works well for shorter workouts, while electrolytes can be useful during longer sessions”
Do you need electrolytes when exercising in hot weather?
Exercising in warmer weather, even in a typical UK summer, increases sweat loss, meaning your body loses both fluids and electrolytes more quickly. This is especially important to consider for summer exercise, whether you’re starting coach to 5k, training for longer runs or using outdoor gym equipment in the heat.
“Running in hot weather increases sweat rates, which means fluid and electrolyte losses happen more quickly. In these conditions, drinks containing sodium and other electrolytes can help support fluid balance and hydration during longer runs,” says Heeral.
Research shows sweat losses can range from around 0.5 to 2.0 litres per hour, increasing in hotter conditions and during prolonged exercise. This means hydration needs can vary significantly depending on the individual, intensity and environment. If you're choosing electrolytes for running in the heat, look for options that contain sodium, as this is the main mineral lost in sweat, along with others like potassium to help support fluid balance.14,15
That said, electrolytes aren't always necessary. “A simple rule is that water works well for shorter workouts, while electrolytes can be useful during longer sessions, heavy sweating or exercise in hot conditions when mineral losses increase,” she adds.
Can dehydration affect your workouts?
Short answer – yes, it can. Even mild dehydration can make exercise feel harder than it should, especially in warmer conditions.
When your body is low on fluids, performance can start to dip, and it becomes more difficult to maintain intensity. That’s why it’s recommended to start your workout already well hydrated.5
If dehydration reaches more than 5% of your body weight, performance can drop by around 30%.1,2 Rehydrating properly after exercise is just as important. In some cases, drinks containing electrolytes can help restore fluid balance more effectively, supporting both recovery and overall performance.
How to tell if you’re dehydrated
If you notice any of the signs below, it’s a good reminder to top up your fluid intake – drinking water regularly throughout the day can help keep you hydrated. Symptoms of dehydration in adults include:7
- feeling thirsty
- dark yellow, strong-smelling urine
- weeing less often than usual
- feeling dizzy or lightheaded
- feeling tired
- a dry mouth, lips and tongue
- sunken eyes
How to tell if you’re too hydrated
Although rarer, symptoms of overhydration may include:8
- cloudy thinking
- nausea and vomiting
- muscle weakness
- spasms or cramps
- headaches
How to prevent overhydrating
- use your thirst cues and urine colour as a guide
- avoid drinking more than one litre of fluid per hour8
Although it's not common to overhydrate, it can happen in rare instances. Avoid drinking too much water in a short time frame, as this is called water intoxication.9
Can being too hydrated impact your workout?
Yes, it can. Your hydration levels can have significant effects on both your physical and mental performance. Both overhydration and underhydration can impair performance and pose a risk to health.10
Electrolytes and exercise FAQs
It often comes down to how long and how intensely you've been exercising, as well as how much you have been sweating. If you have done a short or moderate workout, water and your usual diet are typically enough. But after longer sessions or exercise in hot weather, electrolytes may help support rehydration.5,6
In most cases, yes. A balanced diet and regular fluid intake will usually provide enough electrolytes for everyday activity and shorter workouts.4 However, during longer or more intense exercise, especially when you are sweating more, your needs can increase.
If your body is low on fluids and electrolytes, you may notice fatigue, muscle cramps, dizziness or a drop in performance. These signs are more likely during longer workouts, intense sessions or exercising in the heat, when sweat losses are higher. If symptoms persist or feel severe, it's important to stop exercising, rehydrate and seek medical advice if needed.
The final say
Electrolytes can be a helpful addition if you’re taking on longer, more intense training – think marathon prep, HYROX or tougher endurance sessions. But for shorter workouts or a few gym sessions each week, you’ll usually get what you need from your diet and regular hydration.
If you’re exercising in warmer conditions or simply want extra support, exploring electrolyte options can be a useful next step. From magnesium waters to electrolyte drinks, our round-up of workout companions can help you find a favourite that fits your routine. Looking to level up your overall routine? Build your own sports nutrition stack to support performance, recovery and wellness.
Disclaimer – This article provides informational advice and is not a substitute for medical care. Curated by experts for accuracy, we take great care to ensure the information is up to date and relevant. However, you should always consult your GP or healthcare professional before using supplements or alternative products, particularly if you have medical conditions or are under supervision.
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