Executive summary
- Definition: serum sodium <135 mmol/L.
- The key primary care question is urgency: symptomatic or severe biochemical hyponatraemia needs emergency admission because treatment and correction rate must be carefully controlled.
- Asymptomatic mild hyponatraemia can sometimes be worked up in primary care if the person is clinically stable and the likely cause is identifiable.
Immediate triage
- Red flags for same-day hospital assessment: confusion, reduced consciousness, seizures, severe headache, vomiting, marked deterioration, or severe biochemical hyponatraemia even if symptoms are subtle.
- Do not attempt rapid correction in the community. Over-rapid correction risks osmotic demyelination.
- If stable and asymptomatic, assess chronicity, review medications, assess volume status, and look for an underlying cause.
Pragmatic primary care work-up
- Medication review is high yield: thiazide and thiazide-like diuretics, SSRIs, carbamazepine, antipsychotics, PPIs, desmopressin and some anticonvulsants commonly contribute.
- Think by volume status: hypovolaemic, euvolaemic (including SIADH), or hypervolaemic states such as heart failure, cirrhosis, or nephrotic states.
- Useful baseline tests: repeat U&Es, glucose, renal function, consider TFTs and cortisol where clinically indicated, and pursue urine studies or secondary care advice if SIADH is suspected.
- Management principle: treat the underlying cause, stop offending drugs if safe, and arrange interval sodium re-checks based on severity and clinical stability.
Frequently asked questions
Can mild asymptomatic hyponatraemia be managed in primary care?
Sometimes, yes. NICE CKS supports primary care assessment where the patient is clinically stable, the hyponatraemia is mild/asymptomatic, and there is a plausible reversible cause such as medication.
What are the common GP-prescribing causes?
Thiazide or thiazide-like diuretics are classic, but SSRIs, carbamazepine, antipsychotics, PPIs, and desmopressin are also important drug causes to review.
What is the key danger in treatment?
Correcting sodium too quickly. That is why symptomatic or severe cases belong in hospital rather than in routine community management.
Transparency
This page is an educational, clinician-written summary of publicly available NICE guidance intended for trained healthcare professionals. It uses original wording (not copied text) and should be used alongside the full NICE source, local pathways, and clinical judgement. Doses provided are for general reference; always check the BNF/SPC.