Osmolality, Serum


The term osmolality refers to the osmotic concentration of a fluid. Sodium, blood urea nitrogen, and blood glucose levels are major factors in determining serum osmolality. The osmolality of serum, urine, or any other body fluid depends on the number of active ions or molecules in a solution. Tests of both serum and urine osmolality can yield important information about a patient’s ability to maintain a normal fluid balance status.


Increased in dehydration, hypercalcemia, tubular dysfunction, and is a very sensitive indicator in early acute renal failure. Decreased in adrenocortical insufficiency, water intoxication, inappropriate ADH secretion.

Sample Type, Quantity & Conditions

2 ml Serum Stability: 3 Days at 2-8 °C

Special Precautions

Needed Tests for calculation: Urea, Glucose, Potassium and Sodium. Calculated

Normal Range

280 - 298 mOsm/Kg Panic values: <240 >330 mOsm/Kg

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