Test Name: Osmolality
Formal Name: Serum Osmolality
Other Names: Serum Osmolality, Osmolality
Normal: 275-295 mOsm/kg. High: Dehydration, Diabetes Insipidus. Low: Water overload, Hyponatremia.
Why Test: To evaluate kidney function, fluid balance, and detect poisoning.
When to Test: Severe dehydration, confusion, head trauma, or suspected antifreeze (ethylene glycol) poisoning.
Test Principle: Freezing Point Depression (Osmometer) or Vapor Pressure.
Q1: Is this the same as sodium levels? A1: No, sodium is one solute; osmolality measures the total concentration of all solutes. Q2: Why check for poisoning? A1: Antifreeze (ethylene glycol) drastically increases osmolality.
