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):
Learn more by checking out our additional educational resources below.