High5 Zero Review UK 2026: Tested and Rated by a Nutritionist

High5 Zero is worth buying for recreational sport and everyday hydration - but it has a real sodium ceiling that endurance athletes need to understand before committing. High5 Zero is one of the most widely stocked effervescent electrolyte tablets in UK sport - available in Tesco, Holland and Barrett, and across most running shops. At roughly 40p per tablet, it sits at the affordable end of a crowded market. What the packaging does not tell you is how that price interacts with the sodium dose, and whether the dose is sufficient for the activity you are doing. That is what this high5 zero review sets out to establish. For a broader look at the category first, our electrolytes guide covers the science behind why sodium, potassium, and magnesium matter.

Clemmie Rose is a registered Nutritional Therapist with clinical experience spanning Google DeepMind, Harrods, and international longevity summits. Her supplement assessments work through the full label - doses against reference values, ingredient form, and what the science actually supports.

High5 Zero delivers a clean, zero-calorie effervescent tablet at a price point that beats most direct competitors. The sodium dose - 250mg per tablet - is adequate for moderate-intensity sessions and everyday hydration. It falls short of the higher-loss scenarios that serious endurance athletes face, where clinical guidance points to 500-700mg of sodium per litre of fluid. For recreational sport, casual hydration, and keto-friendly daily use, the value case is strong. For long-distance running, cycling events, or hot-weather training, the sodium ceiling is a real limitation.

Overall rating: 3.8 / 5. Worth it for recreational use. Sodium-limited for endurance.

High5 is a UK-based sports nutrition brand established in 1994 and best known among British endurance athletes for its energy gels, bars, and hydration products. The Zero range is the brand's dedicated electrolyte tablet line: zero added sugar, zero significant calories, designed to dissolve in water and replace minerals lost through sweat.

Zero tablets contain a blend of sodium, potassium, and magnesium - the three minerals most relevant to exercise hydration. They also contain a small amount of vitamin C (28mg per tablet). The calorie count is 0 kcal per tablet. This is a zero-sugar, zero-calorie product, with the 'zero' referencing both added sugar and calorie content.

Testing involved: dissolving one tablet in 750ml of water per the label instruction, assessing fizz time, visual dissolution, taste across three flavours (citrus, berry, and tropical), and reviewing the full nutritional label against current EFSA mineral reference values and NHS guidance on fluid and electrolyte balance. Competitor label data (SiS Hydro, Nuun Sport) was cross-referenced from current UK retail listings.

High5 Zero is part of a product family that also includes the best electrolytes for athletes who train at higher intensities - but the Zero range specifically is positioned at daily hydration and moderate exercise rather than race-day fuelling.

At 250mg of sodium per tablet, High5 Zero sits squarely in the middle of the mainstream electrolyte tablet range - but whether that dose is sufficient depends entirely on what you are doing. The NHS guidance on salt and nutrition recommends adults consume no more than 2,300mg of sodium per day, but during exercise the loss rate varies significantly. A moderate training session of 60 minutes might result in losses of 300-800mg of sodium depending on body size, sweat rate, and conditions. A long-distance endurance event in warm conditions can push losses considerably higher.

High5 Zero provides 250mg of sodium per tablet, intended to be dissolved in 750ml of water. That is a sodium concentration of approximately 333mg per litre of fluid - a figure that sits within the range of what sports nutrition position statements consider appropriate for general exercise hydration. The EFSA's reference value for adequate sodium intake is 2,000mg per day for adults; Zero's contribution per serving is a meaningful supplement to dietary intake rather than a clinically corrective dose.

The honest read: 250mg per tablet is adequate for most recreational use. It covers a one-hour gym session, a light morning run, or everyday background hydration without food. For athletes doing two to three hours of sustained output in warm conditions - cyclists on a summer sportive, marathon runners, open-water swimmers - a single tablet per 750ml is unlikely to replace what is being lost. Those athletes need either two tablets per bottle or a higher-sodium product.

For comparison, the Science in Sport Hydro review is directly relevant here: SiS GO Hydro contains 345mg of sodium per tablet (higher than Zero), while Nuun Sport provides 300mg per tablet. High5 Zero's 250mg sits below both on sodium dose but is the most affordable option at its price point among mainstream UK tablet formats.

The potassium (70mg) and magnesium (56mg) contributions are modest against BDA sports nutrition guidance on mineral reference values of 3,500mg and 375mg per day respectively for potassium and magnesium. These are supplementary rather than meaningful corrections - which is appropriate for a hydration tablet, not a mineral supplement.

Zero contains only 9mg of calcium per tablet (1.1% of the reference intake) - a modest contribution that is unlikely to meaningfully supplement dietary intake for athletes on plant-based diets where calcium may already be lower. Sweat calcium losses are real but typically modest in short sessions, so this is not a critical gap for recreational use.

Verdict on electrolyte profile: sufficient for its stated purpose; limited for high-sodium-loss endurance scenarios.

Effervescent tablets live or die on dissolution and taste. High5 Zero dissolves cleanly in approximately 90 seconds at room temperature - slightly faster in cool water, slightly slower when cold from the refrigerator. The fizz is moderate: enough to signal something is happening, not so aggressive that it creates carbonation in the drink. After three minutes, the tablet is fully dissolved and the drink is still.

Citrus is the benchmark flavour. It reads as lemon-lime with a clean citrus note, a mild sweetness from sucralose (the sweetener used across the range), and a faint mineral undertone that is characteristic of sodium-containing hydration products. It is not sharp. It is not sweet in the way a sports drink is sweet. The aftertaste is mild and fades within 30 seconds.

Berry is more polarising. The sweetener note is more detectable in this flavour - an observation consistent with wider consumer feedback on berry variants in the effervescent electrolyte category. It is not unpleasant, but drinkers who are sensitive to sweetener aftertaste will notice it more here than in citrus or tropical.

Tropical is the mildest-tasting of the three tested. The fruit note is subtle and the sweetener signature is less prominent. This is the better choice for drinkers who want electrolytes without strong flavour.

The key complaint found across user reviews of High5 Zero relates to sweetener aftertaste, particularly in non-citrus flavours. This is not unique to High5 - sucralose is widely used across the effervescent electrolyte category because it survives the dissolution process without breaking down. The perception of sweetener aftertaste is highly individual. If you are already comfortable with sugar-free products, you will likely not notice it. If you are transitioning from flavoured water or plain electrolytes, you may find it more pronounced in the first few uses.

One format point: the tablets are large (standard effervescent size, around 12g per tablet) and the tube packaging is convenient for gym bags and cycling jersey pockets. The tube cap is secure. There is no powder mess. These are meaningful practical advantages over powder formats for on-the-go use.

High5 Zero is available in 20-tablet and larger multipack formats from the High5 website, Amazon UK, Holland and Barrett, Tesco, and specialist running retailers.

Current price points (verified 2026, subject to change):

The best per-tablet value is through Amazon multipacks, where the cost drops to around 22p. The official High5 site prices a 20-tablet tube at £7.99, which works out to around 40p per tablet. There is no permanent High5 discount code available to the public - promotional codes do appear through run club partnerships, affiliate channels, and seasonal sales, but they are time-limited.

Against SiS GO Hydro (from £0.30 per tablet) and Nuun Sport (from £0.45 per tablet), High5 Zero is competitive on price, particularly in multipack format. The question of value depends on sodium requirement: at 250mg sodium for around 40p per tablet (single tube), or 22p per tablet (multipack), High5 Zero offers a practical entry point to electrolyte supplementation.

If you are training for endurance events and need closer to 500mg of sodium per 750ml, using two High5 Zero tablets (around 80p single-tube, 44p multipack) is still a cost-effective option, with the added benefit of matching the sodium dose more closely to guidance for high-sweat-rate exercise.

The electrolytes for keto use case is particularly strong: zero sugar, zero calories, convenient tablet format, and a reasonable sodium contribution for daily use outside of training. For keto followers managing electrolyte depletion from reduced carbohydrate intake, two tablets per day at around 80p (single tube) or 44p (multipack) is a practical and low-cost intervention.

Athletes doing sustained endurance work over 90 minutes in warm conditions, or anyone with a clinically documented need for higher sodium replacement, should consider a higher-sodium product. Two High5 Zero tablets per bottle is a practical workaround at modest additional cost. For a structured comparison across the wider category, the full best electrolytes UK guide covers options across sodium doses and formats.

Balance Journal is published alongside Balance Coffee, founded by James Bellis. A note on caffeine and hydration: if you train in the mornings, pairing a well-sourced coffee with good hydration practice matters - the diuretic effect of caffeine is real but modest at habitual consumption levels. The best coffee beans UK guide covers options that suit pre-training routines without excessive caffeine load.