Hyponatraemia Cause Algorithm
Systematically identifies the cause of hyponatraemia using plasma osmolality, urine osmolality, and urine sodium. Guides targeted treatment.
Score interpretation
→ Hypertonic: treat hyperglycaemia (Na corrects as glucose normalises); isotonic: check triglycerides/protein; dilute urine: restrict water; treat primary polydipsia
→ Hypovolaemic: IV 0.9% saline; hypervolaemic (CCF/cirrhosis): fluid restrict + treat underlying; euvolaemic + concentrated urine + U-Na >20: check TFTs, cortisol, medications; likely SIADH
→ SIADH: fluid restriction 800-1000ml/day; tolvaptan if severe/refractory; demeclocycline second-line; treat underlying cause (malignancy, CNS, pulmonary); rate of correction: max 8-10 mmol/L per 24h (risk of osmotic demyelination)
Interpretation bands for the Hyponatraemia Cause. Apply clinical judgement and local guidance.
References
Related
Curated clinical cross-links plus same-class fallbacks.
- Sodium Chloride 3% (Hypertonic Saline) · Hypertonic Electrolyte Solution — ICP/Hyponatraemia Management
- Sodium Bicarbonate · Alkalising Agent / Electrolyte
- Sodium Bicarbonate 8.4% · Electrolyte Buffer
- Prednisolone (Oral — General Medicine) · Oral Corticosteroid
- Thiopental Sodium · Barbiturate Induction Agent
- Calcium Gluconate · Electrolyte — Calcium Supplement
- Falls Assessment in Older Adults · NICE CG161 2013
- Anaemia Investigation · BSH / NICE
- Lower Respiratory Tract Infection (Primary Care) · NICE NG138 / NICE antimicrobial guidance
- Hypertension Management · NICE NG136 2019
- Hyperkalaemia Management · UK Kidney Association Guidelines 2020; NICE CKD Guidelines
- Rhabdomyolysis · Renal Association 2018; UpToDate 2024
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.