Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX
Initial investigations for a patient presenting with hyponatraemia should include:
- Repeat serum sodium measurement to confirm hyponatraemia and assess for rapid changes, which may indicate a need for urgent admission NICE CKS.
- Assessment of volume status clinically to classify the hyponatraemia as hypovolaemic, euvolaemic, or hypervolaemic NICE CKS.
- Measurement of urinary sodium concentration and urinary osmolality to help determine the underlying cause, although interpretation can be difficult especially if the patient is on diuretics or has renal impairment NICE CKS.
- Blood tests including plasma potassium, urea, creatinine, and glucose to assess electrolyte balance and renal function NICE CKS.
- Consider measurement of venous blood acid–base status and chloride concentration if shock or hypovolaemia is suspected NICE CG84.
- Review of current medications that may contribute to hyponatraemia and stopping any non-essential ones if appropriate NICE CKS.
If the cause remains unclear after these initial investigations, referral to a specialist (endocrinologist or nephrologist) is recommended for further evaluation NICE CKS.