1. What is Measured Serum Osmolality?

Measured serum osmolality is a laboratory test that determines the concentration of solute particles in blood serum. It is directly measured using osmometry and reflects the body's water balance and kidney function.

2. How Does the Calculator Work?

This calculator simply displays the measured lab value you enter, as the measurement is performed directly by laboratory equipment:

Where:

• Lab Value — Direct measurement from osmometry (mOsm/kg)

3. Importance of Osmolality Measurement

Details: Serum osmolality is important for evaluating fluid and electrolyte balance, diagnosing conditions like dehydration, diabetes insipidus, or toxin ingestion, and monitoring treatment effectiveness.

4. Using the Calculator

Tips: Enter the measured osmolality value from your lab report in mOsm/kg. The value must be greater than 0.

5. Frequently Asked Questions (FAQ)

Q1: What is the normal range for serum osmolality?
A: Normal range is typically 275-295 mOsm/kg, though exact ranges may vary by laboratory.

Q2: How does measured osmolality differ from calculated osmolality?
A: Measured osmolality detects all osmotically active particles, while calculated estimates only the major ones (Na, glucose, BUN).

Q3: When is osmolality testing indicated?
A: For evaluation of hyponatremia, altered mental status, suspected toxin ingestion, or disorders of water balance.

Q4: What causes increased osmolality?
A: Dehydration, hyperglycemia, alcohol intoxication, mannitol therapy, or uremia.

Q5: What causes decreased osmolality?
A: Overhydration, SIADH (Syndrome of Inappropriate ADH Secretion), or severe hyponatremia.