title: "Electrolytes and Hydration for Training: What You Actually Need to Know" description: "Evidence-based guide to electrolytes. Learn sodium, potassium, magnesium roles, sweat rates, over-hydration risks, drink types, and practical recommendations for training." date: "2026-03-29" author: "Seb" category: "Nutrition" tags: ["hydration", "electrolytes", "sodium", "potassium", "training", "performance"] affiliateDisclosure: true
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Electrolyte drinks are everywhere. Brands like LMNT, Precision Hydration, and High5 have built entire businesses around the claim that plain water isn't enough — you need sodium, potassium, and minerals to optimise training and recovery.
There's truth in this, but it's wrapped in significant marketing overstatement. Electrolytes matter for some people in some situations. For others, they're completely unnecessary.
This guide cuts through the noise and tells you exactly when electrolytes matter and when you're just buying expensive water.
What Are Electrolytes?
Electrolytes are minerals that carry an electrical charge and regulate fluid balance, muscle contractions, and nerve impulses. The key ones:
- Sodium: Regulates fluid balance, blood pressure, muscle contractions
- Potassium: Counteracts sodium, regulates heart rhythm, muscle function
- Magnesium: Muscle function, energy production, recovery
- Calcium: Muscle contraction, bone health
Your body maintains electrolyte balance tightly — it's not optional. When you sweat, you lose electrolytes (especially sodium), which disrupts this balance. The question isn't whether electrolytes matter (they do) but whether you need to supplement them.
Sweat Rate and Electrolyte Loss
Sweat isn't pure water. It contains sodium (20-80 mmol/L) and trace amounts of potassium and magnesium. Heavy training causes significant fluid and electrolyte loss.
Example: A 90kg male doing 90 minutes of hard training might sweat 1.5-2L. If sweat contains 50 mmol/L sodium, that's 75-100mmol sodium lost (~1.7-2.3g).
This loss is real. Your body needs to replace it.
However: Most of this replacement happens through normal eating. A single slice of bread contains ~400mg sodium. A banana contains ~400mg potassium. Normal meals provide abundant electrolytes.
The supplementation question is only relevant in specific scenarios (see below).
The Over-Hydration Problem: Hyponatraemia
Here's what most people don't know: it's possible to drink too much plain water, and it's dangerous.
Hyponatraemia occurs when blood sodium concentration drops below 135 mmol/L, typically from excessive plain water consumption without adequate electrolyte intake. Symptoms include nausea, confusion, seizures, and in extreme cases, cerebral oedema and death.
This is rare in healthy people doing normal training, but it happens. Specifically:
- Ultra-endurance events (marathons, triathlons over 3 hours)
- Excessive plain water intake without food
- Hot conditions with profuse sweating
The fix is simple: don't drink excessive plain water during training. Drink when thirsty, not by rigid schedule. Include electrolytes (from food or drinks) if training longer than 90 minutes in hot conditions.
Drink Types: Isotonic vs Hypotonic vs Hypertonic
Drinks are classified by osmolarity (solute concentration):
Isotonic Drinks
Osmolarity: 280-310 mOsm/L (matches blood)
Composition: 6-8% carbohydrate, 20-30mmol/L sodium
Absorption: Balanced — good fluid absorption without drawing water into the gut
Best for: Most people doing general training, 60-120 minutes
Examples: Most commercial sports drinks (Gatorade, Powerade, High5)
Cost: £0.80-1.50 per 500ml bottle, or £0.20-0.40 per homemade litre
Hypotonic Drinks
Osmolarity: <280 mOsm/L
Composition: <6% carbohydrate, may have electrolytes
Absorption: Faster fluid absorption, good for maximum hydration
Best for: Short training (under 60 minutes), very hot conditions, those wanting pure hydration without much carbohydrate
Examples: Diluted juice, water with a pinch of salt
Cost: Cheap (DIY option)
Hypertonic Drinks
Osmolarity: >310 mOsm/L
Composition: 8%+ carbohydrate, high electrolytes
Absorption: Slower fluid absorption (draws water into the gut), but more carbohydrates and minerals
Best for: Endurance training (2+ hours), post-workout recovery
Examples: Concentrated drinks, thick smoothies
Cost: Variable, usually more expensive
When Electrolytes Actually Matter
Short Training (Under 60 Minutes)
Plain water is sufficient. You're not losing enough fluid or electrolytes to require supplementation. Electrolytes here are marketing.
Exception: Hot weather (>25°C) and very heavy sweaters. Even then, a pinch of salt in water is enough.
General Training (60-120 Minutes)
An isotonic drink with electrolytes is useful — it provides hydration, carbohydrate for energy, and salt to maintain electrolyte balance. This is where sports drinks make sense.
Cost vs benefit: A homemade isotonic drink (below) is ~£0.20 per litre. Commercial equivalents are £0.80-1.50. The DIY version works identically.
Endurance Training (2+ Hours)
Electrolytes become genuinely important. You're losing substantial sodium and carbohydrate. A drink providing 20-30mmol sodium and 6-8% carbohydrate is evidence-supported.
This is where premium brands like Precision Hydration or LMNT have a case.
Hot Weather or Profuse Sweat Loss
Add sodium even for shorter training in hot conditions. 1/4 teaspoon of salt in 500ml water provides ~400mg sodium — often enough.
Homemade Isotonic Drink Recipe (Costs ~£0.20 per Litre)
If you're doing 60-120 minute training blocks and want an isotonic drink without premium pricing:
Ingredients:
- 1 litre water
- 5-6 tablespoons sugar (or glucose powder)
- ¼ teaspoon salt (~500mg sodium)
- Juice of 1 lemon (optional, for flavour)
Nutrition: 6% carbohydrate, ~20mmol/L sodium — perfect isotonic profile
Cost: Sugar (1p) + salt (<1p) + lemon (5p) + water negligible = ~7p per litre
Taste: Not as polished as commercial drinks, but it works identically.
Mixing: Dissolve salt and sugar in hot water first, then cool and add remaining water.
Make 2 litres weekly, store in the fridge.
Commercial UK Options
If you prefer convenience:
Budget Friendly
- High5 Zero (sugar-free, electrolytes): £8-10 per 20 servings (~£0.40-0.50 per serving) — Shop on Amazon UK
- MyProtein Electrolyte (basic formula): £12-15 per month — Shop on Amazon UK
Mid-Range
- SIS Go Electrolyte (specifically formulated): £15-20 per month — Shop on Amazon UK
- Precision Hydration (personalised sodium): £12-18 per month depending on formula — Shop on Amazon UK
Premium
- LMNT (minimal carbs, high electrolytes): £25-30 per month — Shop on Amazon UK
- Liquid IV (multiple electrolytes): £20-25 per month — Shop on Amazon UK
LMNT vs Precision Hydration: Are They Worth It?
Both brands position themselves as premium options.
LMNT: Minimal carbohydrate (1g), high sodium (1000mg per serving). Marketed for "optimisation" and endurance.
Precision Hydration: Customised sodium based on sweat rate and individual loss. Higher carbohydrate (4-8g).
Reality: For most people doing standard training, neither is necessary. A homemade isotonic drink or High5 does 95% of what they do at 1/10 the cost.
Where they make sense: If you're doing serious endurance events (2+ hours regularly) and want to optimise every variable, Precision Hydration's customisation might be worth it. LMNT is good for those doing very low-carb training or wanting convenience, but it's premium pricing for something you can DIY.
Practical Hydration Timing
Before training: 400-500ml water, 2-3 hours before. Allows absorption and bathroom time.
During training (under 60 minutes): Water, no need for electrolytes. Drink to thirst.
During training (60-120 minutes): Isotonic drink (sports drink or homemade), 500-750ml per hour depending on sweat rate.
During training (2+ hours): Hypertonic drink with higher carbs and sodium, 500-750ml per hour.
Post-training: 500ml drink with carbohydrate and electrolytes within 30 minutes. Or eat food — a meal covers both.
Individual Sweat Rate Calculation
Everyone sweats differently. Calculate yours:
- Weigh yourself before training
- Train for 1 hour (don't drink)
- Weigh yourself after training (dry off sweat)
- Weight loss = sweat loss (minus urine loss, assume ~100ml)
Example: Lost 1.2kg = roughly 1100ml sweat loss per hour.
This person needs to drink ~800-1000ml per hour (you don't want to perfectly replace sweat loss or you'll be running heavy).
Use this to dial in your personal hydration strategy.
Potassium and Magnesium: Do You Need Supplementation?
Sodium is the primary electrolyte lost in sweat. Potassium and magnesium losses are minimal and easily replaced through normal eating.
Potassium: One banana provides 400mg. Not needed as supplementation unless you're doing ultra-endurance or have specific medical issues.
Magnesium: Minimal loss in sweat. Your magnesium status depends on diet, not hydration. If you're deficient, supplement magnesium (glycinate or citrate) separately, not through sports drinks.
Bottom line: Electrolyte drinks focus on sodium and carbohydrate. That's correct — those are the relevant variables. Potassium and magnesium are side issues.
Common Mistakes
Rigid hydration plans: "Drink 250ml every 15 minutes." Drink to thirst. Individual sweat rates vary massively.
Over-hydrating on plain water: Especially in longer training. Add electrolytes or you risk hyponatraemia.
Buying expensive electrolyte drinks for 30-minute sessions: Unnecessary. Save money and use plain water.
Ignoring post-workout rehydration: If you've lost significant fluid, rehydrate post-training with electrolytes and carbs. This matters more than during-training hydration for most people.
Not considering individual needs: A 60kg female and 100kg male sweating in different conditions have completely different hydration needs. Personalise.
The Bottom Line
Plain water is sufficient for training under 60 minutes. For 60-120 minute sessions, an isotonic drink (6-8% carbohydrate, 20-30mmol sodium) improves performance and hydration — commercial or homemade works identically. For endurance training (2+ hours), electrolytes become genuinely important.
Make a homemade isotonic drink for ~£0.20 per litre (sugar, salt, water) and use it for standard training. It works as well as premium brands costing 10x more. Reserve commercial options for convenience or specific protocols (ultra-endurance, heavy sweating in heat).
Hydration is important. Electrolytes matter in specific contexts. But you don't need fancy branded supplements to optimise either. Homemade solutions work perfectly and cost nearly nothing.