Appropriate Tests


Hypernatraemia is not usually seen unless the individual has a defective thirst mechanism or is unable to drink.

Electrolytes, Osmolality, Creatinine, Urea. Electrolytes urine, Osmolality urine.

Artefactual result

See Table 1.

Inadequate fluid intake, especially
  • Confusion/coma


Excessive fluid loss, especially
  • Respiratory tract
    • Mechanical ventilation
    • Hyperpnoea
  • Skin
    • Sweating
  • Kidneys
    • Reversal of urinary tract obstruction
    • Diabetes insipidus


Excessive salt intake, especially
  • Intravenous saline
  • Intravenous sodium bicarbonate
  • Incorrect infant formula


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