🩺 General MedicineRenal / ElectrolyteStudentInternResident

Hyponatraemia

Also known as: low sodium · low Na · SIADH

A low serum sodium — the commonest electrolyte disturbance. Assess severity, acuity and volume status, and correct carefully to avoid osmotic demyelination.

Source · Reviewed 2026-08-15 · v1.0— AI-assisted draft — verify against the cited guideline before clinical use.

⚕️ Education only — not medical advice. Verify against the latest official guideline and your local protocol; confirm every drug dose against the cited source before clinical use.

Who gets it

Common in the elderly, hospitalised patients, and in heart/liver/kidney failure, SIADH (drugs, lung/CNS disease, cancer), and with diuretics.

Red flags — escalate / refer

Severe symptoms (seizures, reduced consciousness, coma) or acute severe hyponatraemia → hypertonic saline urgently.
Over-rapid correction risks osmotic demyelination syndrome — respect the correction-rate limit.

Work-up / diagnosis

1Assess symptoms, acuity, and volume status (hypo-, eu-, or hypervolaemic).
2Send paired serum and urine osmolality and urine sodium; review medications.
3SIADH is a diagnosis of exclusion (euvolaemic, concentrated urine, no other cause).

Management — overview

Severe/symptomatic (seizures, coma): careful boluses of hypertonic (3%) saline to raise sodium just enough to control symptoms — with strict correction-rate limits.
Hypovolaemic: isotonic saline + treat the cause. Hypervolaemic (heart/liver/kidney failure): fluid restriction + treat the cause. Euvolaemic/SIADH: fluid restriction + treat the cause.
Correct SLOWLY (respect the maximum daily sodium rise) and recheck sodium frequently.
Stop contributing drugs.

In-depthFull dosing & advanced protocol

Drug dosing

Hypertonic (3%) saline

Severe symptomatic hyponatraemia

Adult dose: Small aliquots to a modest sodium rise sufficient to stop symptoms; monitor closely
Route: Intravenous

Caution: Do NOT correct too fast — limit the rise per 24 h to avoid osmotic demyelination syndrome.

ICMRStandard Treatment Workflows (STWs), India — Dept. of Health Research & ICMR (2022+) ↗

Isotonic saline or fluid restriction (by type)

Non-emergency correction

Adult dose: Isotonic saline (hypovolaemic); fluid restriction (euvolaemic/hypervolaemic)
Route: IV / oral restriction

ICMRStandard Treatment Workflows (STWs), India — Dept. of Health Research & ICMR (2022+) ↗

Correction limits & SIADH

Respect the maximum correction rate; if overcorrected, re-lower sodium (e.g. with dextrose ± desmopressin) to prevent demyelination.
SIADH: fluid restriction first; treat the underlying cause; consider additional measures per specialist advice.
Match treatment to acuity: acute symptomatic hyponatraemia needs prompt hypertonic saline; chronic needs slow correction.

ICMRStandard Treatment Workflows (STWs), India — Dept. of Health Research & ICMR (2022+) ↗

References

Guidelines change. If something here is out of date, tell us — we keep these current.

🚩 Report outdated / suggest update

More protocols

HypertensionPersistently raised arterial pressure (≥140/90 mmHg) — a leading, modifiable cause of stroke, heart attack, heart failure and kidney disease.DengueAn Aedes-borne viral febrile illness. Most cases self-limit, but plasma leakage can cause severe dengue — early recognition of warning signs and careful fluid therapy save lives.MalariaA mosquito-borne protozoal (Plasmodium) febrile illness. In India P. vivax and P. falciparum predominate; prompt diagnosis and species-specific treatment prevent severe disease.

Loading…

👤 Who gets it

🚩 Red flags — escalate / refer

🔎 Work-up / diagnosis

🧭 Management — overview

💊 Drug dosing

Hypertonic (3%) saline

Isotonic saline or fluid restriction (by type)

📈 Correction limits & SIADH

📚 References

More protocols

👤 Who gets it

🚩 Red flags — escalate / refer

🔎 Work-up / diagnosis

🧭 Management — overview

💊 Drug dosing

Hypertonic (3%) saline

Isotonic saline or fluid restriction (by type)

📈 Correction limits & SIADH

📚 References

More protocols

Who gets it

Red flags — escalate / refer

Work-up / diagnosis

Management — overview

Drug dosing

Correction limits & SIADH

References

Who gets it

Red flags — escalate / refer

Work-up / diagnosis

Management — overview

Drug dosing

Correction limits & SIADH

References