What are the recommended management strategies for acute versus chronic hyponatraemia?

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

Posted: 16 August 2025Updated: 16 August 2025 Guideline-Aligned (High Confidence) Clinically Reviewed
Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX

Management of Acute Hyponatraemia:

  • Admit immediately if onset is less than 48 hours or if serum sodium is less than 125 mmol/L, or if symptomatic or hypovolaemic.
  • For acute hyponatraemia with moderate or severe symptoms, administer hypertonic saline to safely raise serum sodium and reduce cerebral oedema risk.
  • In acute hyponatraemia with mild or no symptoms, stop non-essential parenteral fluids and medications that provoke hyponatraemia, and treat the underlying cause.

Management of Chronic Hyponatraemia:

  • For chronic hyponatraemia without moderate or severe symptoms, stop non-essential supplementary fluids and medications that provoke hyponatraemia, and treat the underlying cause.
  • In hypervolaemic patients, fluid restriction is recommended to prevent further fluid overload.
  • In hypovolaemic patients, restore extracellular volume with 0.9% saline infusion.
  • For syndrome of inappropriate antidiuretic hormone secretion (SIADH), fluid restriction is advised; if no clear cause is found, further imaging may be needed, and specialist treatment such as tolvaptan may be considered under supervision.

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