Does an isotonic drink replace gels?

It can cover part of your carbs while hydrating, but for high hourly needs it often has to be topped up. The key is to count total carbs, drink + gels included.

Can I make my own isotonic drink?

Yes, with water, a carb source and a pinch of salt, keeping a concentration close to isotonic. Test the recipe in training before using it in a race.

Isotonic or plain water?

Plain water on short, cool efforts; isotonic on long or intense efforts where you need energy and sodium on top of hydration.

Hydration6 min

Isotonic drink: what is it for?

An isotonic drink is one whose concentration of dissolved particles is close to that of blood, which promotes efficient absorption of water and carbs. In practice, it often combines hydration, electrolytes and energy in a single sip. But it isn't always necessary: it all depends on the effort's duration, the heat and your carb needs. This guide clarifies when it's genuinely useful.

When an isotonic drink helps

Isotonic drinks shine on long and/or intense efforts where you need fluids, sodium and carbs at once: they simplify logistics by combining all three. On a short, easy run, water is enough and an isotonic adds little. Watch the concentration: too strong (close to hypertonic), it can cause GI discomfort. Follow the stated dosages and dilute properly.

Isotonic, hypotonic, hypertonic

'Tonicity' describes the drink's concentration relative to blood. An isotonic drink has a similar concentration, allowing fast absorption of water and carbs — a good hydration/energy compromise. A hypotonic one, more dilute, favours pure hydration. A hypertonic one, more concentrated, delivers plenty of carbs but can slow gastric emptying and hinder hydration. The right choice depends on your priority: drinking, or refuelling.

Practical checklist

Isotonic mainly on long/intense efforts (water + sodium + carbs)
Plain water on short, easy runs
Follow the stated dilution to stay isotonic
Don't stack a concentrated gel + concentrated drink
Brand and dosage validated in training

Common mistakes

Using an isotonic on a short run where water would do
Mixing the drink too concentrated and causing GI discomfort
Taking a gel with an isotonic and stacking too high a sugar load
Relying on the isotonic for all your carbs on a very long effort without checking the amounts
Switching brand on race day without having tested it

FAQ

Hydration7 min

Running hydration: water, sodium and electrolytes

Hydration isn't just drinking more: duration, heat and your sweat rate all matter.

Read the guide

Product guides6 min

Energy gel or energy drink: which one to pick?

The right format depends on when you use it, your digestion and the carb dose you're aiming for.