Hyponatraemia and hypernatraemia
Sodium disorders are water disorders. Osmolality, urine osmolality and urine sodium sort the causes; symptoms and duration set the speed of treatment; correction limits prevent osmotic demyelination.
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Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Serum sodium reflects water balance, not total body sodium. Hyponatraemia is too much water relative to sodium; hypernatraemia is too little.
- Hyponatraemia (under 135 mmol/L) is the commonest electrolyte disorder in hospital, present in up to 30% of inpatients. The European 2014 guideline grades it as mild 130 to 134, moderate 125 to 129 and profound under 125 mmol/L.
- Treat symptoms, not the number. Severe symptoms need hypertonic saline now. Chronic, mild symptoms need the cause found and slow correction.
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Sources
- Fluid and electrolyte disorders (Therapeutic Guidelines)AU/NZTherapeutic Guidelines Ltd
- Spasovski G et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia (ESE, ESICM, ERBP). Eur J Endocrinol 2014;170:G1-G47European Society of Endocrinology, European Society of Intensive Care Medicine and European Renal Best Practice, 2014 (still the current European guideline at November 2026)
- Verbalis JG et al. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. Am J Med 2013;126(10 Suppl 1):S1-S42American Journal of Medicine, 2013
- Baek SH et al. Risk of overcorrection in rapid intermittent bolus vs slow continuous infusion therapies of hypertonic saline for patients with symptomatic hyponatremia (SALSA). JAMA Intern Med 2021;181:81-92JAMA Internal Medicine, 2021
- Refardt J et al. A randomized trial of empagliflozin to increase plasma sodium levels in patients with the syndrome of inappropriate antidiuresis (SALT-TRIAL). J Am Soc Nephrol 2020;31:615-24Journal of the American Society of Nephrology, 2020
- Last updated
- 14 November 2026
What changed
- 14 November 2026 Personal emails, About story and Australian-style copy