Sodium / Electrolyte Sodium deficiency
Symptoms, at-risk groups, and clinical context for sodium / electrolyte sodium deficiency. Sourced from NIH Office of Dietary Supplements and StatPearls.
Sodium deficiency from inadequate dietary intake is essentially unheard of in the modern world — most Americans consume ~3,400 mg/day, well above the 2,300 mg UL. Hyponatremia (serum <135 mmol/L) is the most common electrolyte disorder in clinical practice, but it's almost always caused by water excess, kidney issues, or medical conditions — NOT low salt intake. The framing here is imbalance, not deficiency.
Common symptoms
- Headache, nausea, vomiting
- Confusion, lethargy, or altered mental status
- Muscle cramps or weakness
- Restlessness or irritability
- Loss of appetite
- Severe acute hyponatremia: seizures, coma, brain swelling
- Endurance athletes — exercise-associated hyponatremia from drinking too much plain water
At-risk groups
- Endurance athletes who drink large volumes of plain water during long events (marathons, ultra-events)
- People with SIADH (syndrome of inappropriate ADH secretion)
- People with congestive heart failure, cirrhosis, or nephrotic syndrome
- People taking thiazide diuretics, SSRIs, antipsychotics, or NSAIDs
- Older adults (impaired water excretion, polypharmacy)
- People with severe vomiting or diarrhea who replace fluids with plain water
- People with adrenal insufficiency
- People with primary polydipsia or extreme low-sodium diets combined with high water intake
When to see a doctor: Sudden confusion, severe headache, or seizures in someone who has been drinking large amounts of water — especially during endurance exercise — should be treated as a MEDICAL EMERGENCY. Note: most US adults should be focused on REDUCING sodium intake, not increasing it. The 2,300 mg/day limit is associated with reduced cardiovascular risk. Very low-sodium diets (<1,500 mg/day) without medical supervision can be problematic for some people.
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Related deficiencies
Nutrients with overlapping symptoms — useful when investigating an unclear clinical picture.