The Ultimate Guide to Electrolytes

The electrolyte market grew by over 35% in the UK in 2024. You probably noticed. They are in every gym bag, every coffee shop fridge, and now apparently in the hands of people who walk from their desk to a meeting and back.

The question nobody seems to be asking: who actually needs them?

I have been advising clients at my private practice, through the wellness supplements space, at the Kyros Project at Google DeepMind, and at The Wellness Clinic at Harrods for several years. In that time, the question I am asked most often about electrolytes is not "which one should I buy." It is "do I actually need this at all?" That is the question this guide exists to answer. We checked every hydration and sodium claim against the NHS, the British Dietetic Association, and EFSA reference values, costed the DIY option against branded powders ourselves, and had it reviewed by our nutrition team.

Some of you do need them. Some of you are spending £40 a month on a problem you do not have. This guide tells you which one you are.

Electrolytes are minerals that carry an electrical charge when dissolved in water. Your body uses that charge to do everything from fire a nerve impulse to contract a muscle to regulate how much water stays inside your cells.

The NHS electrolyte test page lists the key ones: sodium, potassium, chloride, magnesium, calcium, phosphate, and bicarbonate. The four that matter most for the supplement conversation are sodium, potassium, magnesium, and calcium.

You lose electrolytes primarily through sweat, urine, and (in significant illness) vomiting and diarrhoea. The amounts matter. A 30-minute walk in mild British weather and a desk job all week? Your food covers it, almost certainly without your help. Run a half marathon in July heat? Different story entirely.

The supplement industry would prefer you did not notice the difference between those two scenarios.

This is the question at the centre of everything. The honest answer depends entirely on your circumstances, so here are the use cases that actually change the answer.

Endurance athletes and high-intensity training

If you are training for 90 minutes or more, particularly in heat, or losing significant sweat volume, supplementing makes sense. The British Dietetic Association's fluid and hydration fact sheet confirms that sodium is the electrolyte most depleted by sweat and the one most likely to affect performance. Sports electrolytes with 500-1,000mg sodium per litre of fluid are appropriate here, not as a daily baseline habit.

For sessions under 60 minutes at moderate intensity: water is sufficient. The evidence does not support supplementing short-duration, low-sweat exercise.

People on ketogenic or low-carbohydrate diets

If you are in the early stages of a ketogenic or fasted eating pattern, electrolytes are not marketing. They are physiology. When carbohydrate intake drops sharply, insulin levels fall and the kidneys begin excreting more sodium and potassium. The result (headaches, fatigue, muscle cramps, brain fog) is what the community calls 'keto flu.' It is a real electrolyte deficit, not a detox symptom. Supplementing sodium (500-1,000mg per day), potassium, and magnesium during the adaptation phase typically resolves it within 48 hours.

Once adapted (usually 3-6 weeks), most people eating a whole-food ketogenic diet can reduce supplementation significantly. Vegetables are high in potassium; meat and fish cover sodium. The need is front-loaded.

People on GLP-1 medication (Mounjaro, Wegovy, Saxenda)

This is the fastest-growing question in my clinic right now. GLP-1 receptor agonists like Mounjaro (tirzepatide) and Wegovy (semaglutide) work partly by significantly reducing appetite. When food intake drops substantially, so does dietary electrolyte intake. Add in any GI side effects (nausea, vomiting, diarrhoea are common in the early weeks) and you have a genuine depletion risk.

The evidence base specific to GLP-1 and electrolytes is still building, but the mechanism is clear: lower food intake and GI losses mean lower electrolyte intake and higher electrolyte losses. If you are on a GLP-1 and eating significantly less than usual, particularly if you are experiencing side effects, speaking to your prescriber or a registered nutritional therapist about targeted supplementation is sensible. A product with sodium, potassium, and magnesium at moderate doses (not LMNT's 1,000mg sodium per serving) is the format to consider.

During and after illness

This is the textbook use case. Vomiting, diarrhoea, high fever, or significant fluid loss from any cause creates real electrolyte depletion quickly. Oral rehydration solutions (ORS) like Dioralyte are pharmaceutical-grade and the appropriate format here, not sports powders. They contain a specific glucose-to-sodium ratio that optimises intestinal fluid absorption. For illness, choose the pharmacy aisle, not the gym supplement shelf.

Coffee drinkers

There is a persistent belief that coffee dehydrates you and depletes your electrolytes. See the dedicated section below, but briefly: the evidence does not support dramatic hydration concern for moderate coffee intake. Your morning americano is not the problem.

Desk workers and general population

For most people sitting at a desk in a temperate climate, eating a reasonably balanced diet, and exercising moderately: you do not need an electrolyte supplement. The food already provides it. The British Dietetic Association recommends 6-8 glasses of fluid daily from any source, and a normal mixed diet covers electrolyte requirements for the general population without supplementation.

For most people at a desk, a daily £1.30 electrolyte sachet solves a problem you do not have.

This one comes up constantly, partly because Balance Coffee is our sister company (we sell coffee, not electrolytes, so this guide has no product to push) and partly because the "coffee dehydrates you" belief is genuinely widespread.

The short answer is: not meaningfully, at moderate intake.

A well-designed randomised controlled trial by Killer et al., published in PLOS ONE in 2014, found no evidence of dehydration with moderate daily coffee intake when comparing coffee to water in regular coffee drinkers. Participants drinking 4 cups a day showed equivalent hydration markers to those drinking only water.

Coffee is a mild diuretic: it does cause you to produce slightly more urine in the short term. But the volume of fluid in the coffee more than compensates for the mild diuretic effect, and regular coffee drinkers develop a partial tolerance to the diuretic effect over time.

What this means practically: two to four cups of coffee a day do not warrant electrolyte supplementation. If you are running a marathon and drinking strong pre-workout espresso in hot weather, the picture gets more complicated. For the daily flat white? You are fine. Drink water alongside it if you like, but you are not creating a deficit that needs correcting with a supplement.

The best greens powders question comes up alongside coffee in a similar framing: "am I offsetting the bad with the good?" The honest answer is the same in both directions. Coffee is not meaningfully bad for hydration. Greens powders are not specifically compensating for coffee. Both are reasonably good habits. Neither cancels the other out.

The supplement industry would prefer you bought the branded sachet at £1.30-£2.50 per serving. Here is what you actually get for that money and what you can make for less.

The DIY electrolyte drink recipe:

Total cost: under 10 pence per serving, if you buy the ingredients in bulk. A 250g tub of Lo-Salt costs around £1.80 at most UK supermarkets.

What a DIY mix does not give you: precise magnesium dosing without buying magnesium powder separately, consistent flavour, travel convenience, or the functional ingredients some premium brands add (taurine, B vitamins, adaptogenic herbs). If you value any of those, the branded option earns its price.

Per-serving sodium comparison (UK market, June 2026):

LMNT's 1,000mg sodium per serving is appropriate for marathon training and excessive for a Tuesday. More is not better here. It is physiology, not marketing.

When to pay for the branded format: you need precise magnesium alongside sodium and potassium; you travel frequently and need sachets; the flavour makes you actually drink enough fluid (compliance matters); you are in a clinical context (GLP-1, keto adaptation) where the measured doses are the point.

When the DIY route wins: you are a moderate exerciser supplementing as a precaution; cost is a consideration; you already buy Lo-Salt and magnesium for other uses.

Most electrolyte marketing glosses over sodium. Let me not do that.

The EFSA dietary reference values for sodium set an adequate intake of 2,000mg sodium per day for adults. UK adults currently consume an average of 8.4g salt (~3,360mg sodium) per day from diet alone (NHS data), well above the recommended maximum of 6g salt (~2,400mg sodium).

Adding a daily high-sodium electrolyte supplement on top of an already sodium-heavy diet is not neutral. For healthy adults with normal kidney function exercising intensely in heat, the extra sodium is processed without issue. For people with hypertension, heart failure, kidney disease, or any condition that affects fluid regulation, adding 1,000mg sodium per day from a supplement is something to discuss with a GP or registered dietitian first.

The precautionary position is sensible: if you do not have a clear physiological need for electrolyte supplementation (endurance sport, keto adaptation, GLP-1 side effects, illness), the additional sodium load from daily supplementation is not risk-free and not necessary. Choose a lower-sodium product (240-400mg per serving) if you are supplementing for general wellness rather than a specific physiological context.

Magnesium is the electrolyte where genuine deficiency is most common in the UK population, more so than sodium. It is worth checking whether your diet covers the recommended 300mg (men) or 270mg (women) daily from food before reaching for any electrolyte supplement.

If you have worked through the use cases above and decided a product is right for you, here is what to look for.

Prioritise the ratio, not the marketing claim. Look at the sodium per serving first. Match it to your use case: 500-1,000mg for endurance sessions lasting 90+ minutes; 200-400mg for general wellness or moderate activity; 1,000mg+ only if prescribed or advised by a sports dietitian for extreme endurance events.

Check the potassium and magnesium, not just sodium. Many budget products skimp on potassium. Aim for at least 100mg potassium per serving. Magnesium above 50mg elemental per serving is a bonus for recovery.

Avoid artificial sweeteners if gut sensitivity is a concern. Some research links sucralose and acesulfame potassium to altered gut microbiome composition; the evidence is not conclusive, but if you are taking electrolytes for GI recovery or are sensitive to artificial sweeteners, choose a stevia-sweetened or naturally flavoured product.

UK-available shortlist for the most common use cases:

A full ranked comparison with scores, third-party testing data, and affiliate links is in our dedicated best electrolytes UK guide, which publishes alongside the children of this cluster.

Sources: NHS electrolyte test reference; EFSA sodium dietary reference values; MedlinePlus electrolytes overview

Makes: 500ml | Cost: under £0.10 per serving

Ingredients:

Method: Combine all ingredients in a glass or bottle. Stir or shake until the salt dissolves fully. Drink within 24 hours if stored in the fridge.

Prices verified June 2026 from brand websites and major UK retailers. Prices subject to change.