Introduction

The reference range for sodium is 135 mmol/L - 145 mmol/L

Interpretation

Causes of hyponatraemia
  • diuretics: thiazides, loop diuretics
  • SIADH
  • diarrhoea, vomiting, sweating
  • IV dextrose, psychogenic polydipsia
  • secondary hyperaldosteronism: heart failure, liver cirrhosis
  • burns
  • Addison's disease
  • diuretic stage of renal failure
  • hypothyroidism

Causes of hypernatraemia
  • dehydration
  • osmotic diuresis e.g. hyperosmolar non-ketotic diabetic coma
  • diabetes insipidus
  • excess IV saline