Importance of Measured Osmolality | Advanced Instruments
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Importance of Measured Osmolality

Direct measurement of body fluid osmolality with a freezing point depression osmometer is the preferred method when reporting osmolality in a clinical setting1.

In practice, physicians use both measured and calculated osmolality to determine a patient’s osmolal gap. The difference between measured and calculated osmolality can be diagnostically significant for conditions such as toxic alcohol ingestion and useful for monitoring patients being treated with osmotically active therapies.

If a laboratory were to solely provide calculated osmolality the physicians could not calculate the osmolal gap to screen for foreign substances.

Measured Osmolality (via Freezing Point Depression Osmometer): 

    • Objective measurement 
    • Accounts for everything that impacts osmolality including
      and osmotically active therapies
    • Has tight tolerances at clinically relevant decision points

Calculated Osmolality: 

    • Highly subjective with over 65 equations in the literature 
    • Misses toxins and medications that impact osmolality 
    • Error could be embedded in each component of the calculation 

Measured Osmolality – Calculated Osmolality = Osmolal Gap

The Importance of Measured Osmolality

For further information on why measured osmolality is an important tool in providing the best care possible for patients, please view our new resource, “The Importance of Measured Osmolality Testing with an In-House Osmometer”.

Importance of Measured Osmolality Webinar

This webinar, organized by Radiometer in partnership with Advanced Instruments, details the importance of measured osmolality. Please note that this webinar is in French.


Make sure you are ready for a quick and accurate turnaround of STAT osmolality test orders with the trusted industry leader in clinical osmometers and osmolality testing.  Our products are based on the gold-standard freezing point depression detection to ensure accurate results for confident reporting.

  1. Eisen, T. F., Lacouture, P. G., Woolf, A.: Serum osmolality in alcohol ingestions: differences in availability among laboratories of teaching hospital, nonteaching hospital, and commercial facilities. Am J Emerg Med 1989; 7:256-259.