Electrolytes or magnesium for rugby cramp?

By Tom Francis·Updated 2026-09-03·3 sources·Editorial policy

They are answers to different questions

An electrolyte drink is a hydration product. Its job is replacing fluid and sodium lost in sweat during and after a match, and sodium is the electrolyte lost in the largest amounts by a long way.

A magnesium supplement is an intake product. Its job is covering a daily reference value of 375mg across a week, a month and a season. One works over a match, the other works over months, and comparing them directly for cramp misunderstands both.

The sodium point

Sweat is mostly water and sodium. Magnesium losses in sweat are real but small in absolute terms next to sodium losses, which is why a drink built for during play leads on sodium and why magnesium in those drinks is usually a token amount.

A player who has drunk only water through a hot pre season session has a sodium and fluid problem before they have a magnesium problem, and an electrolyte drink is the right tool for that specific situation.

Neither has a cramp claim

This is the part both categories skate over. There is no authorised health claim for preventing or treating cramp in the UK, for electrolyte drinks, magnesium, salt tablets or anything else.

Magnesium does carry authorised claims for normal muscle function, normal protein synthesis, reduction of tiredness and fatigue and electrolyte balance, at 15 percent of the reference intake or above. Electrolyte drinks generally carry no health claim at all, only a hydration positioning. Neither of those is a cramp claim.

What the cramp evidence actually points at

The best supported explanation for exercise associated cramp is neuromuscular fatigue, where the reflexes controlling contraction shift under accumulated load. That fits cramp arriving after 60 minutes, hitting fit players, and releasing the moment the muscle is stretched.

Under that model neither product is the lever. Conditioning for the actual demands of the match, managing match load in the weeks after a lay off, and sensible hydration across the day are the things that move it.

Using both sensibly

There is no interaction and no reason to choose. A player can take a daily magnesium serving for intake and use an electrolyte drink around hot or long sessions for hydration.

Futuro Labs Magnesium Glycinate is the intake half of that at 22p a day, providing 300mg of elemental magnesium, which is 80 percent of the reference value. The hydration half is a match day decision that depends on conditions rather than a year round purchase.

Reading a sports drink label

Electrolyte products are labelled loosely compared with supplements, so the same method applies with an extra step.

Find the sodium figure per serving, in milligrams, and check what a serving actually is. Some products quote per 500ml and some per litre, which changes everything. Then check whether the magnesium figure is meaningful or decorative: a drink providing 12mg of magnesium is providing about three percent of the 375mg reference value, which is below the 15 percent threshold at which any magnesium claim can be made at all.

That threshold is the useful test. If a drink cannot legally carry a magnesium claim, the magnesium in it is a marketing ingredient rather than a functional one. Futuro Labs Magnesium Glycinate sits at 80 percent of the reference value for comparison, at 22p a day.

When a drink is genuinely worth it

Electrolyte products get bought year round and are worth it in a narrow set of situations, which is worth naming because the alternative is buying them every week.

A long session in genuine heat, particularly in pre season. A double session day where the gap is short. A player who has been identified as a heavy or salty sweater. And a match followed closely by another fixture, where fluid has to be replaced faster than food alone manages.

Outside those, ordinary food with normal salt and drinking across the day covers it for almost every club player. Futuro Labs Magnesium Glycinate at 22p a day handles the daily intake question that a drink was never designed for, and the two decisions can be made independently.

Where to go next

• Does magnesium stop cramp in rugby?The full answer on cramp, the fatigue model and what actually reduces it.
• Futuro Labs Magnesium Glycinate: the full labelElemental content, NRV, both pack sizes and cost per day.
• Magnesium for rugby playersSweat loss, training volume and what the authorised claims cover.

Questions players ask

Sources

• EFSA register of nutrition and health claims
• National Diet and Nutrition Survey, gov.uk
• Committee on Toxicity, magnesium