Electrolytes at Altitude — What You're Losing and How to Replace It
Every liter of sweat contains sodium, potassium, chloride, and magnesium — the minerals your body needs for nerve and muscle function. At altitude, you lose more fluid through breathing alone (respiratory loss doubles), plus sweat on exertion. Replacing water without replacing electrolytes dilutes your blood sodium — the hyponatremia trap that mimics and worsens AMS.
What You're Losing
| Electrolyte | Per Liter of Sweat | Why You Need It | Deficiency Symptoms |
|---|---|---|---|
| Sodium | ~900–1,400mg | Fluid balance, nerve signals, blood pressure | Cramps, nausea, confusion, hyponatremia |
| Potassium | ~200–400mg | Muscle contraction, heart rhythm | Cramps, weakness, irregular heartbeat |
| Chloride | ~1,000–1,500mg | Pairs with sodium for fluid balance | Rarely deficient alone; follows sodium |
| Magnesium | ~10–20mg | Muscle relaxation, energy, sleep | Cramps, restless legs, poor sleep |
When You Need Them
- Hard sweat days — hours of climbing in sun; sweat loss >1L needs electrolyte replacement, not just water
- Above 4,000m — increased respiratory loss on top of sweat; daily electrolyte supplementation makes sense
- Vomiting or diarrhea — massive electrolyte loss; ORS (not sports drinks) is the correct replacement
- Muscle cramps starting — the classic sign; sodium first, magnesium for persistent night cramps
- Post-trek recovery — replenish deficits after multi-day depletion
ORS vs Sports Drinks vs Tablets
| Type | Best For | Sodium Content | Practical Notes |
|---|---|---|---|
| WHO ORS packets | Diarrhea/vomiting — medical-grade replacement | ~1,700mg/L — highest | We stock these; the real-deal rehydration formula, not a sports drink |
| Electrolyte tablets | Daily trek use — convenient | ~300–600mg/tablet | Nuun, LMNT, SaltStick — drop in water; good for prevention |
| Sports drinks (Gatorade) | Moderate exertion | ~300–400mg/L — low | Too much sugar, not enough sodium for serious dehydration |
| Salt packets + water | Emergency field fix | Variable | A pinch of salt in water + food is better than plain water alone |
| Coconut water | Moderate replacement | ~250mg/L + potassium | Available in Kathmandu; not on the trail |
The Hyponatremia Trap — Why "Just Drink Water" Fails
- Dilution is the danger — drinking liters of plain water replaces volume but not sodium; blood sodium drops, symptoms mimic AMS
- The altitude factor — respiratory water loss doubles at altitude; you lose more than the sweat you see
- The symptoms overlap — headache, nausea, confusion, fatigue; hyponatremia looks like AMS until you check the intake pattern
- The fix — electrolytes WITH water; the combination is the requirement, not either alone
- Food is the backup — salty meals (soup, dal bhat with extra salt) replace electrolytes through diet when supplements run out
Daily Electrolyte Strategy for Treks
- Morning start — begin the day with an electrolyte dose in your first water bottle; the base level sets the day up
- Hard sweat days — add a tablet every 2-3 hours of climbing; the schedule replaces the guesswork
- Above 4,000m daily — respiratory loss makes supplementation worthwhile even without visible sweat
- Illness escalation — vomiting or diarrhea switches you to ORS-grade replacement immediately; the formula matters at that severity
- Evening recovery — a dose with dinner replaces the day's losses; the overnight recovery benefits from the replenishment
Common Questions
Why Water Alone Is Not Enough
Trekking produces sweat — sweat contains sodium, potassium, and other electrolytes that water alone does not replace. The trekker drinking plain water exclusively risks hyponatremia (low sodium) — the weakness, headache, and confusion that can mimic altitude illness. Electrolyte replacement (ORS, electrolyte tablets, salted foods) maintains the balance that water alone cannot.
Sources on the Trail
ORS packets (available at pharmacies and teahouses), electrolyte tablets/powders, the salted soup and food that provides sodium naturally, and the water-with-added-electrolytes approach. For most trekkers, the food provides adequate electrolytes; for heavy sweaters or those with GI losses, supplementation matters. The tea is fluid; the electrolyte source is the extra step.
The Sweat Replacement
Trekking produces sweat — the exertion plus the altitude's respiratory demands produce more sweat than the sedentary baseline. The sweat contains sodium, potassium, and other electrolytes that must be replaced. The plain water only replaces the water; the electrolytes must come from the food or the supplementation.
When You Need More Than Food
For normal trekking with adequate food intake, the food covers the electrolytes. For heavy sweaters, hot conditions, GI losses (vomiting, diarrhea), or prolonged exertion — the electrolyte supplementation (ORS, electrolyte tablets/powders) prevents the hyponatremia and the cramping that the electrolyte depletion produces. The supplementation is for the high-loss situation, not the routine trek.
When They Matter
Electrolytes matter during: heavy sweating (the trek's exertion plus the heat), the diarrhea or vomiting (the losses that the fluids alone do not replace), and the prolonged exertion that depletes the sodium. For the standard trekking day, the food provides adequate electrolytes; for the extreme conditions or the GI illness, the supplementation helps.
What to Use
The oral rehydration salts (ORS — the WHO formulation for the diarrhea/vomiting losses) for the GI illness; the electrolyte tablets or the powder for the sweat losses during exertion; the salty food (the soups, the salty snacks) that provides the electrolytes naturally. The over-supplementation (the excessive sodium or potassium) is the different problem.
The Homemade ORS
The WHO ORS recipe — the 1 liter of water + 6 teaspoons of sugar + half teaspoon of salt — the homemade rehydration solution when the commercial packets are unavailable. For the remote trek, the recipe that produces the ORS from the common ingredients.
The Sodium Focus
Sodium is the critical electrolyte for the trekking — the sweat losses deplete the sodium, the overhydration dilutes it, and the altitude's physiology changes the balance. For the trek that produces heavy sweating or the GI losses, the sodium replacement is the priority.
The Replacement
Electrolyte replacement — the ORS that replaces the sodium, the potassium, the glucose; the sports drinks that are less precise; the electrolyte tablets that are portable. For the trek that produces the electrolyte losses, the replacement that maintains the balance.
The Overhydration Risk
Overhydration (the hyponatremia) can be caused by the excessive plain water — the water without the electrolytes that dilutes the sodium. For the trek, the electrolyte balance that matters more than the pure water volume.
The Sodium Focus
Sodium is the key electrolyte for the trek — the sweat that loses the sodium plus the water that dilutes. For the hydration that is water-only, the sodium deficit that develops.
The ORS
Oral rehydration solution — the sodium + potassium + glucose that replaces the losses. For the significant dehydration or the diarrhea, the ORS that is more effective than the water alone.
The Sodium
Electrolyte sodium — the primary that is lost in the sweat. For the electrolyte replacement, the sodium that is the priority.
The ORS
ORS (oral rehydration solution) — the sodium + the glucose that maximizes the absorption. For the significant dehydration, the ORS that is the standard.
The Tablet Cost
Electrolyte tablet cost — the ~ $0.30-0.80/tablet (the Nuun or the similar). For the trek, the lightweight that is convenient.
The Powder Cost
Electrolyte powder — the ORS ~ $0.20 or the sports drink powder ~$0.50/serving. For the volume, the powder that is economical.
The Tablet vs. Powder
Electrolyte form — the tablet ~$8-15, the powder ~$5-10 (the carried that is chosen). For the trek, the light that is preferred.
The Homemade
Homemade ORS — the salt+sugar free (the emergency that is improvised). For the unprepared, the kitchen-mixed that works.
The Tablet
Electrolyte tablet — the ~$0.30-1/dose (the Nuun that is carried). For the trek, the packed that is the kit.
The Homemade
Homemade ORS — the salt+sugar (the free that is the fallback). For the depleted, the mixed that is the cheap.
What is hyponatremia and how do I prevent it on a trek?
Dangerously low blood sodium from drinking too much plain water without electrolyte replacement — it dilutes your sodium. Symptoms mimic and worsen AMS: nausea, headache, confusion. Prevention: add electrolytes (tablets, ORS, or salty food) to your water on hard sweat days; do not just chug water.
Are sports drinks enough for trekking?
Not for serious dehydration — Gatorade-type drinks are too much sugar and too little sodium (~300-400mg/L vs the ~1,700mg/L of ORS). Fine for moderate exertion; insufficient for diarrhea, vomiting, or hours of hard sweating. Use proper electrolyte tablets or WHO ORS.
What is the difference between ORS and electrolyte tablets?
ORS (oral rehydration salts) is the medical-grade formula for diarrhea/vomiting — highest sodium content, designed for clinical dehydration. Electrolyte tablets (Nuun, LMNT) are for prevention and daily use — convenient, adequate for sweat loss, but not strong enough for illness-level depletion.
How do I know if I need electrolytes or just water?
Check the sweat — if you are sweating hard for hours, if you see white salt residue on clothes or skin, if you are cramping, or if water alone is not fixing the washed-out feeling, you need electrolytes. The "just water" advice fails on hard days; the salt loss needs replacement.
Can I get electrolytes on the trail in Nepal?
Limited — Kathmandu has pharmacies and some outdoor shops stock tablets; on the trail, the selection thins. The reliable option: salt packets from meals plus water. Carry your preferred form from Kathmandu; do not depend on teahouse stock for electrolyte needs.
