Electrolytes Dosage Calculator
Sodium, potassium, magnesium, and chloride — the minerals lost in sweat that govern hydration, nerve conduction, and muscle contraction. Inadequate replacement is the primary cause of exercise-associated muscle cramps and hyponatraemia.
What is Electrolytes?
Electrolytes are ionised minerals that regulate osmotic pressure, action potential propagation, and muscle contraction. In an athletic context, the four most critical are sodium (Na⁺, primary extracellular cation), potassium (K⁺, primary intracellular cation), magnesium (Mg²⁺, muscle relaxation and ATP cofactor), and chloride (Cl⁻, osmotic balance). Sweat electrolyte losses vary enormously between individuals (sodium losses range from 460–1,840 mg/L of sweat), making personalised replacement strategies essential. The critical distinction: most electrolyte products are designed for replacement during/after exercise, not enhancement above normal levels. Hyponatraemia (dangerously low sodium) is the primary risk of inadequate sodium replacement in endurance events > 4 hours — it causes nausea, headache, seizures, and in severe cases, death. It is paradoxically more common in slower athletes who over-drink hypotonic fluids without sodium replacement. Conversely, muscle cramps in athletes are multifactorial but electrolyte depletion (particularly sodium and magnesium) is a primary modifiable cause.
How to Take Electrolytes
**During exercise (> 60 min):** 500–1,000 mg sodium + 200–400 mg potassium + 50–100 mg magnesium per hour of sustained exercise in hot conditions, dissolved in 500–750 ml water. **Post-exercise rehydration:** 1.5× the fluid volume lost (measured by pre/post weight) with a sodium-containing electrolyte solution — plain water dilutes plasma sodium and inhibits the thirst response. **Low-carb / keto athletes:** Significantly higher electrolyte needs — 3,000–5,000 mg sodium, 3,000–4,500 mg potassium, and 300–500 mg magnesium daily during keto adaptation (insulin reduction causes increased renal sodium excretion).
Timing Recommendations
**Before:** Pre-hydrate with 400–600 ml electrolyte water 2 hours before exercise if training in heat. **During:** Begin electrolyte intake within the first 30 minutes of exercise lasting > 60 minutes — do not wait for thirst, which is a late dehydration signal. **After:** Prioritise sodium-containing fluids within 30 minutes of finishing; avoid plain water alone for 2+ hours post-exercise until plasma osmolality is normalised.
Potential Side Effects & Safety
Excess sodium intake: hypertension risk in sodium-sensitive individuals at chronically high intakes (> 5,000 mg/day from all sources). Excess potassium: hyperkalaemia (dangerous cardiac arrhythmia risk) in individuals with renal impairment — kidneys normally excrete excess potassium efficiently. Excess magnesium: osmotic diarrhoea. GI distress with concentrated electrolyte products taken without adequate fluid.
Who should avoid Electrolytes?
Renal disease: impaired potassium excretion makes high-potassium electrolyte supplements dangerous — use only under nephrology guidance. Heart failure or hypertension on sodium-restricted diets: consult your cardiologist before using high-sodium sports drinks. Aldosterone disorders (Conn's syndrome, Addison's disease): abnormal electrolyte regulation requires medical management rather than supplementation.
Best Stacks with Electrolytes
Electrolytes + carbohydrates (30–60 g/hour glucose/fructose blend) is the evidence-based endurance fuel strategy — sodium enhances intestinal glucose absorption via co-transporter SGLT1. Electrolytes + creatine: optimal hydration status enhances muscle creatine uptake and reduces intracellular osmotic stress. For keto athletes: electrolytes + MCT oil addresses both electrolyte and ketone fuel needs simultaneously.
Scientific References
All dosage recommendations are grounded in peer-reviewed research.
- 1American College of Sports Medicine position stand: Exercise and fluid replacement
Medicine & Science in Sports & Exercise · 2007
- 2Sodium supplementation and exercise-associated hyponatraemia during endurance racing
British Journal of Sports Medicine · 2011
Electrolytes Dosage Calculator
Fixed dosage — independent of body weight
Your recommended daily dosage
Formula: 500–1,000 mg sodium/hour exercise | adjust upward in heat, high sweat rate, or keto diet
Safety notes
- Renal disease: impaired potassium excretion — high-potassium electrolytes require medical clearance.
- Hyponatraemia risk in events > 4 hours: DO NOT drink plain water only — always include sodium.
- Begin electrolyte intake within 30 min of exercise start — do not wait for thirst.
- Keto/low-carb athletes need 2–3× more sodium and potassium than standard recommendations.
- Concentrated electrolyte products must be diluted in adequate water to prevent GI distress.
This calculator provides general guidance only. Always consult a qualified healthcare professional before starting any supplement.