Osmolal gap is the difference between:

Osmolal gap is the difference between:

• A. The ideal and real osmolality values
• B. Calculated and measured osmolality values
• C. Plasma and water osmolality values
• D. Molality and molarity at 4°C

Answer: (B)

The osmolal gap is the difference between the measured osmolality and the calculated (estimated) osmolality. In the lab, osmolality is often estimated from major solutes using a standard formula (for example, incorporating sodium, glucose, and BUN). The measured osmolality comes from an osmometer. Subtracting the calculated value from the measured value yields the osmolal gap. A small gap is normal; a larger gap points to unmeasured osmotically active substances, such as alcohols or glycols, being present.

The osmolal gap is the difference between the measured osmolality and the calculated (estimated) osmolality. In the lab, osmolality is often estimated from major solutes using a standard formula (for example, incorporating sodium, glucose, and BUN). The measured osmolality comes from an osmometer. Subtracting the calculated value from the measured value yields the osmolal gap. A small gap is normal; a larger gap points to unmeasured osmotically active substances, such as alcohols or glycols, being present.