For clinical reference only — does not replace local trust guidelines or clinical judgement.
‹ Blood Results
Blood Results

Hyponatraemia

Hyponatraemia

Severity
Range
  • Mild
    Na 130–134
  • Moderate
    Na 125–129
  • Severe
    Na < 125 or symptomatic
🧠

Neuro / endocrine (SIADH) Causes

Stroke, head injury, SAH, meningitisPituitary surgerySmall-cell lung cancer / brain tumour (PTHrP, ADH)HypothyroidismAddison's / cortisol deficiency
🫁

Respiratory Causes

Pneumonia (especially Legionella)TBLung malignancy → SIADHCOPD
❤️

Cardiac (hypervolaemic) Causes

Congestive cardiac failureConstrictive pericarditis
🫀

Hepatic / GI Causes

Cirrhosis with ascitesVomiting, diarrhoea, NG lossesHigh-output stoma / fistulaPancreatitis
🫘

Renal Causes

CKD / nephrotic syndromeSalt-wasting nephropathyAdrenal insufficiency
💊

Drugs Causes

Thiazide diureticsSSRIs, TCAs, antipsychoticsCarbamazepine, oxcarbazepinePPIsDesmopressin, MDMA, opioids
🧪

Intake / spurious Causes

Primary polydipsiaBeer potomania, tea-and-toast dietPseudohyponatraemia (hyperlipidaemia, paraproteins)Hyperglycaemia (translocational)