Excess osmolal gap in diabetic ketoacidosis explained.

Even in the absence of detectable ethanol or visible lipemia, a large plasma osmolal gap is the usual finding in cases of diabetic ketoacidosis. This gap decreases to an insignificant value within 20 h of treatment. Detailed biochemical analysis of six cases showed that, on average, the gap could be almost wholly accounted for by an increase in acetone, a decrease in the plasma water fraction, and smaller increments in amino acids and glycerol. Calculated plasma osmolality can seriously underestimate the true value in diabetic ketoacidosis, and so some previously observed anomalies may be explained.