Lactate and the osmolar gap

Although the teaching case report in the March 27 issue on a negative anion gap and elevated osmolar gap resulting from lithium overdose1 is interesting, I identified the following concern.

In the third paragraph from the end of the report, the authors listed lactate as one of the potential causes of an elevated osmolar gap that they excluded. It is unfortunate that they perpetuated this common misperception of the role of lactate. An elevated lactate concentration does not account for an elevated osmolar gap because the lactate is accounted for in the osmolality calculation by multiplying the sodium concentration by 2.