Much less common (except in critically ill patients)

Causes

• Dehydration
  • Low water intake - e.g. elderly patient CVA unable to drink
• Diabetes mellitus - diuresis
• Diabetes insipidus - Increases renal water loss
• Other causes of fluid loss - excess sweating, burns, pancreatitis, D&V
• Excess IV saline

Clinical features

Non-specific:

• nausea
• vomitting
• confusion
• fever

Diabetes insipidus:

• Polydipsia
• Polyuria
• Thirst

Severe hypernatraemia - convulsions and seizures