Short answer. For a normal one-hour session, water is usually enough. Electrolytes matter more in heat, for long sessions, two-a-days and heavy sweaters. Weigh yourself before and after training and aim to keep losses below about 2% of bodyweight (ACSM).
Why heat changes things
Training in a hot gym, or at a camp in Thailand, means more sweat, and sweat carries sodium as well as water. The American College of Sports Medicine (ACSM) position stand on fluid replacement suggests avoiding a water deficit of more than about 2% of bodyweight during exercise, and warns that drinking far more than you sweat can dilute blood sodium (hyponatraemia).
A simple check
The ACSM approach is practical: weigh yourself before and after a session, without sweaty clothes. Each kilogram lost is roughly a litre of sweat not replaced. Use that to plan how much to drink next time, rather than following a fixed number.
What the EU allows a sports drink to say
“Carbohydrate-electrolyte solutions contribute to the maintenance of endurance performance during prolonged endurance exercise. Carbohydrate-electrolyte solutions enhance the absorption of water during physical exercise.”
Authorised EU health claim. Condition of use: 80–350 kcal per litre from carbohydrates (at least 75% from high-glycaemic carbohydrates), 20–50 mmol/l sodium (460–1150 mg/l) and an osmolality of 200–330 mOsm/kg water.
Those claims apply only to drinks that meet all three conditions. Zero-sugar electrolyte tablets do not meet them, so they cannot carry these claims.
What to buy
Carbohydrate-electrolyte powder
For two-a-day training or long sessions in heat: a powder with sugar and sodium, mixed to the strength on the pack.
- Compare sodium per litre with the 460–1150 mg/l range above
- Mix to the stated strength: stronger is not better
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On Amazon, prefer the brand's own storefront or listings shipped and sold by Amazon, and check that the label matches the brand's website. Look for a batch-tested logo (for example Informed Sport) if you compete.
Electrolyte tablets
Sodium and other minerals with little or no sugar, for shorter sessions or for people who get their carbohydrates from food.
- Easy to carry to the gym
- Check sodium per tablet: amounts vary a lot between brands
A note on weight cuts
Deliberate dehydration to make weight is a medical risk, especially in heat. This guide is about hydrating for training. Weight cuts belong with your coach and a medical professional.
FAQ
Do I need electrolytes or is water enough?
For a normal one-hour session, most guidance says water is enough. Sodium matters more for long sessions, heavy sweaters, two-a-days and training in heat.
How much should I drink during training?
There is no single number. ACSM suggests weighing before and after training and aiming to keep losses below about 2% of bodyweight, without drinking more than you sweat.
Sources
- Sawka MN et al. (2007), ACSM position stand: exercise and fluid replacement, Med Sci Sports Exerc
- EFSA (2011), Scientific opinion on carbohydrate-electrolyte solutions
- EU Register of nutrition and health claims (European Commission)
- Maughan RJ et al. (2018), IOC consensus statement: dietary supplements and the high-performance athlete, Br J Sports Med
More supplements guides
- Creatine monohydrateThe one authorised performance claim, 3–5 g a day, and the weight-class catch.
- Whey proteinDo you need it, how much per day, and whey vs plant vs casein.
- Caffeine and pre-workout3–6 mg/kg in studies, EFSA's 200 mg / 400 mg safety levels, and label checks.
- Collagen and jointsWhat the early evidence shows, and the vitamin C claim that is authorised.