Causes of Hypernatremia - Differential Diagnosis Algorithm

Hypernatremia - Excess free water loss, Serum Sodium >145 mmol/L

High Urine Osmolality > 300 mmol/kg

 • Hypertonic saline administration

 • Osmotic diuresis (see Polyuria scheme) e.g., mannitol, glucosuria

Low Urine Osmolality < 300 mmol/kg

 • Diabetes Insipidus

Hypodipsia - Decreased intake of water

 • Decreased level of consciousness

 • No access to water

GI loss

 • Watery Diarrhea

Insensible loss

 • Burns

 • ICU patients

 • Fever

 • Inadequate intake for exercise-related loss

 • Hyperventilation



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