Electrolytes, explained

The short version

Electrolytes are minerals that carry an electric charge in your body fluids — mainly sodium, potassium, magnesium, calcium and chloride. They decide where water goes. Drink plain water and much of it passes through; drink water with the right minerals and your body holds and uses more of it where it's needed.

When water alone is enough

For most of a normal, air-conditioned day, it is. Thirst is a good guide, meals supply minerals, and no pack — ours included — is necessary. Anyone who tells you otherwise is selling something.

When it isn't

Long or heavy sweating, work in heat, illness that costs you fluids, a small appetite, or a day where you simply can't eat and drink normally. In those cases the limiting factor stops being water and starts being the minerals that left with it — sodium first, then potassium and magnesium.

How to read a pack

Ignore the front-of-pack 'total electrolytes' sums. Read three numbers: sodium (the main event), potassium, and magnesium — and check what form the magnesium is in. Our mineral-by-mineral guide shows what a meaningful dose looks like for each.