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SIADH (Inappropriate ADH Secretion)

Also known as: syndrome of inappropriate antidiuretic hormone · SIAD

Inappropriate ADH secretion causing water retention and EUVOLAEMIC hyponatraemia with concentrated urine — a common cause of hyponatraemia. It is a diagnosis of exclusion (normal thyroid, adrenal and renal function, no diuretics).

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

Caused by CNS disorders, chest disease (pneumonia, TB), malignancy (especially small-cell lung — ectopic ADH), and many drugs (SSRIs, carbamazepine and others).

Red flags — escalate / refer

Severe symptomatic hyponatraemia (seizures, marked confusion, coma) → emergency (hypertonic saline in a controlled setting); a rapid fall in sodium is more dangerous than the absolute value.

Work-up / diagnosis

1Confirm the criteria — hyponatraemia with LOW plasma osmolality, an INAPPROPRIATELY concentrated urine (high urine osmolality) and urine sodium not low, in a clinically EUVOLAEMIC patient.
2Ensure normal thyroid, adrenal and renal function and no diuretics; then find the cause (drugs, chest/CNS/malignancy).

Management — overview

Treat the cause and stop offending drugs.
FLUID RESTRICTION is the mainstay for chronic/mild SIADH.
Severe symptomatic hyponatraemia → cautious hypertonic saline in a monitored setting; correct sodium SLOWLY (avoid osmotic demyelination); second-line options (vaptans, demeclocycline) in selected cases.

In-depthFull dosing & advanced protocol

Drug dosing

Fluid restriction (mainstay)

Chronic/mild SIADH

Adult dose: Restrict per protocol; treat the cause
Route: Oral intake limit

Caution: Correct sodium slowly — over-rapid correction causes osmotic demyelination.

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

Cautious hypertonic saline (severe symptoms)

Severe symptomatic hyponatraemia

Adult dose: In a monitored setting, controlled rate per protocol
Route: Intravenous

WHOWHO Model List of Essential Medicines (electronic EML) (2025 (24th)) ↗

Euvolaemic; correct slowly; find the cause

SIADH is euvolaemic hyponatraemia and a diagnosis of exclusion.
Never correct sodium too fast — risk of osmotic demyelination (central pontine myelinolysis).
Fluid restriction is first-line; always hunt for a drug/chest/CNS/malignant cause.

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.

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👤 Who gets it

🚩 Red flags — escalate / refer

🔎 Work-up / diagnosis

🧭 Management — overview

💊 Drug dosing

Fluid restriction (mainstay)

Cautious hypertonic saline (severe symptoms)

📈 Euvolaemic; correct slowly; find the cause

📚 References

More protocols

👤 Who gets it

🚩 Red flags — escalate / refer

🔎 Work-up / diagnosis

🧭 Management — overview

💊 Drug dosing

Fluid restriction (mainstay)

Cautious hypertonic saline (severe symptoms)

📈 Euvolaemic; correct slowly; find the cause

📚 References

More protocols

Who gets it

Red flags — escalate / refer

Work-up / diagnosis

Management — overview

Drug dosing

Euvolaemic; correct slowly; find the cause

References

Who gets it

Red flags — escalate / refer

Work-up / diagnosis

Management — overview

Drug dosing

Euvolaemic; correct slowly; find the cause

References