Refers to the difference between measured and calculated serum osmolality.
Elevation in osmolal gap reflects presence of an osmotically active substance in the blood not accounted for by the usual calculation of the osmolality.
Equal to measured serum osmolality minus calculated serum osmolality, with a normal result less than 10.
Causes with a normal anion gap are poisoning with isopropanol, acetone, mannitol, diethyl ether, while with an elevated anion gap poisoning agents include methanol, ethylene glycol, formaldehyde and paraldehyde.