Symptoms, at-risk groups, and clinical context for sodium / electrolyte sodium deficiency. Sourced from NIH Office of Dietary Supplements and StatPearls.
Sodium deficiency from low dietary intake is rare: US adults average about 3,400 mg a day, above the 2,300 mg level the National Academies set for chronic disease risk reduction (no upper limit was set). Low blood sodium (hyponatremia) is usually caused by excess water intake, kidney problems or other medical conditions rather than low salt intake. In endurance athletes, it comes mainly from drinking more fluid than is lost.
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 fluid during long events
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 doctorSudden confusion, severe headache or seizures in someone who has been drinking large amounts of water, especially during endurance exercise, needs emergency medical care. Most US adults eat more sodium than recommended and benefit from eating less, not more; the National Academies advise cutting back if intake is above 2,300 mg a day.