Hyponatremia — The Overhydration Nobody Warns You About
Everyone warns about dehydration — almost nobody warns about the opposite. Drinking excessive plain water without electrolytes dilutes your blood sodium, causing hyponatremia: headache, nausea, confusion, seizures, coma. It mimics altitude sickness and kills trekkers who think they're being healthy. Drink to thirst, not to a schedule.
How It Happens
- Forced hydration — "drink 4–5 liters daily" advice causes some trekkers to chug plain water constantly
- Plain water + heavy sweating — you sweat out sodium; replacing with plain water dilutes what's left
- Long duration — 8–10 hour trekking days mean hours of sweating + hours of drinking — the imbalance compounds
- Sodium dilution — blood sodium drops below 135 mmol/L; brain cells swell with water — that's why it affects thinking and coordination
Symptoms — The Cruel Overlap with AMS
- Early: headache, nausea, bloating, fatigue — looks exactly like mild AMS or dehydration
- Progressive: confusion, disorientation, muscle cramps, vomiting — looks like worsening AMS
- Severe: seizures, coma — at this stage it's life-threatening
- The difference: overhydrated trekkers have excessive urine output (clear, frequent) vs dehydration's dark, scant urine — and they feel bloated, not thirsty
Drink Smart — The Right Rules
- Drink to thirst, not to schedule — your body's thirst mechanism is well-calibrated; don't override it with "must drink X liters" rules
- Electrolytes for long days — days over 6 hours of sweating need sodium; ORS sachets, electrolyte tablets, or salted food — not just water
- Eat real food — dal bhat, soup, salted snacks — food provides the electrolytes water can't
- Urine check — clear urine all day means you're overhydrating; pale yellow is the target
- Bloated feeling = stop drinking — if you feel waterlogged and bloated, you don't need more water, you need electrolytes
The Paradox
Both dehydration AND hyponatremia cause headache, nausea, and fatigue — and both look like altitude sickness. The treatment is opposite: dehydration needs fluids; hyponatremia needs fluid restriction and electrolytes. If you're drinking 4+ liters daily and feeling worse, not better — you might be drowning yourself. Come in; a blood test settles it in an hour.
The Hydration Mistakes Trekkers Actually Make
- The "5-liter rule" trap — generic advice to drink a fixed amount regardless of thirst; the trekker forcing down liters when not thirsty is creating the problem
- Water-only days — eight hours of plain water with no electrolyte source is how the sodium drops; ORS or salted snacks must accompany the water
- The summit-day binge — some trekkers front-load water on summit day "for energy"; they summit with a sodium deficit instead
- Ignoring thirst to avoid bathroom stops — the opposite extreme; underhydrating because toilet stops are inconvenient is its own problem
- The wrong fix — feeling bad on the trail and chugging more water because "it must be dehydration" — if it's hyponatremia, you just made it worse
What We Do at the Clinic
- Serum sodium + electrolytes — the lab answer to whether you are overhydrated, dehydrated, or actually fine
- AMS differentiation — the symptoms overlap so cleanly that the blood test is the definitive answer; we run it when the picture is ambiguous
- Electrolyte correction — ORS protocol and dietary salt for mild cases; the fix is measured, not aggressive
- Severe case escalation — confusion, seizures, or altered consciousness from hyponatremia goes to hospital care; we do not manage that at clinic level
- Prevention consult — if you are planning a long trek, we review your hydration plan and the electrolyte strategy that fits your route and exertion level
Common Questions
The Overhydration Danger
Hyponatremia — low blood sodium from excessive water intake without electrolyte replacement — is the counterintuitive danger: the trekker who drinks too much plain water dilutes the sodium, producing weakness, confusion, seizures in severe cases. The advice to "hydrate" taken to excess produces the opposite problem.
The Balance
Hydrate to thirst, not to a forced schedule — the kidneys regulate hydration if electrolytes are adequate. Use ORS or electrolyte supplements with water for prolonged sweating; the plain water only is insufficient for the electrolyte losses. The headache/nausea/confusion after heavy water intake with minimal food is the pattern — drink less, replace electrolytes.
The Overhydration Danger
Hyponatremia — dangerously low sodium from excessive water intake without electrolyte replacement — produces symptoms that mimic AMS: headache, nausea, confusion, weakness. The trekker who drinks excessive plain water at altitude produces the hyponatremia that is indistinguishable from AMS clinically. The treatment differs — the hyponatremia worsens with more water.
Prevention
Drink to thirst, not beyond — the excessive intake (the "drink as much as possible" myth that is now debunked) produces the problem. Electrolytes with the intake (the food provides, or the electrolyte supplementation for the heavy sweaters) maintains the balance. The hydration that is appropriate is not the overhydration that is harmful.
Exercise-Associated Hyponatremia
EAH — the exercise-associated hyponatremia — occurs when the athlete drinks excessive hypotonic fluids (plain water) during prolonged exercise. The trekker who drinks 3+ liters per hour of the plain water without the electrolyte replacement dilutes the sodium. The symptoms (nausea, headache, confusion, the weight gain from the fluid overload) overlap with the AMS.
The Drinking Guidance
Drink to thirst — the thirst mechanism is the evolved regulation that prevents the overhydration. The myth of "drink as much as possible" produces the hyponatremia. The urine color (light yellow is adequate; the clear urine is overhydration) is the practical indicator. For the trekker, the thirst-guided drinking is the safe approach.
The Overhydration Danger
Hyponatremia is caused by the excessive water intake — the drinking that exceeds the sodium losses. For the trek that encourages the constant drinking, the hyponatremia that results is the risk that the dehydration guidance overlooks.
The Prevention Balance
Prevention: drink to thirst, the electrolyte drinks (the ORS that replaces the sodium), the salty foods during the exertion, and the awareness that the water is not unlimited in its safety.
The Overhydration
Hyponatremia is caused by the excessive water intake — the drinking that exceeds the sodium losses. For the "drink constantly" advice that some follow, the overhydration that results.
The Prevention
Prevention: drink to thirst, the electrolyte drinks that replace the sodium, and the awareness that the water alone can be dangerous in excess.
The Mechanism
Hyponatremia mechanism — the excessive water intake that dilutes the sodium. For the trek that produces the large water intake, the overhydration risk.
The Prevention
Hyponatremia prevention: the electrolyte that is added (the sodium that replaces the loss), the intake that is moderated (the not excessive water), and the symptoms that are monitored.
The Symptoms
Hyponatremia symptoms — the nausea, the headache, the confusion, the seizure (the severe that is the emergency). For the excessive water intake, the hyponatremia that is suspected.
The Sodium
Hyponatremia sodium — the serum that is low (<135 that is the diagnostic). For the suspected, the measurement that confirms.
The Electrolyte Cost
Electrolyte cost — the tablet ~ $0.30-0.80, the ORS ~$0.20 (the cheap that prevents). For the heavy sweater, the electrolyte that is added.
The Food Sodium
Sodium from food — the free (the salty snack, the soup that is included). For the prevention, the eating that is adequate.
The Electrolyte
Hyponatremia prevention — the electrolyte ~$5-15 (the sodium that is the guard). For the heavy-sweater, the supplemented that prevents.
The Food Sodium
Sodium food — the salty-snack ~$1-3 (the free-ish that works). For the trek, the eaten that maintains.
The Sodium
Hyponatremia sodium — the ~$5-15 (the salt-tablet/ salty-snack that is the counter). For the over- drinker, the carried that is the prevention.
The Clinic
Severe hyponatremia — the ~$100-400 (the confused that is the emergency). For the symptomatic, the urgent that is the care.
How much water is actually enough on a trek?
Drink to thirst, not to a fixed number — that is the correct rule and the one most guides get wrong. Pale yellow urine is the target, not "clear all day." If you are forcing liters past your thirst, you are diluting sodium. Electrolytes (ORS, salted food, electrolyte tablets) matter as much as water on long days.
Is hyponatremia really as dangerous as dehydration?
More so in some ways — both cause headache and nausea and both look like altitude sickness, but hyponatremia directly swells brain cells and causes seizures and coma. The trekker drinking 5 liters of plain water daily because "hydration is important" is the one at risk. The fix is electrolytes, not more water.
How do I tell overhydration from altitude sickness?
Check your urine output. AMS and dehydration both mean reduced, dark urine. Hyponatremia means frequent, clear urine plus bloating. If you are urinating a lot, your urine is clear, and you still feel terrible with headache and nausea — stop drinking plain water and get electrolytes.
Should I stop drinking water if I suspect hyponatremia?
Reduce plain water, yes — but do not dehydrate. The fix is electrolytes, not fluid restriction to zero. ORS sachets (available at every pharmacy and teahouse) restore sodium balance while keeping you hydrated. If you feel waterlogged and bloated, the issue is sodium, not water volume.
Can you test for it at the clinic?
Yes — a serum sodium level is a routine blood test we run same-day. If you have been hydrating aggressively and feel worse rather than better, the number answers it in an hour. Treatment for mild cases is electrolyte correction; severe hyponatremia (confusion, seizure) is a hospital problem, and we do not sit on it.
