Assessing ketosis: approaches and pitfalls.

Although the mechanism of action of the ketogenic diet (KD) remains unknown, ketones have been used as a marker of efficacy. Acetoacetate, acetone, and beta-hydroxybutyrate can be measured in urine, blood, and breath. The value of these measures is reviewed in this paper. Future brain measures hold promise as markers of efficacy, but research focused on the mechanisms of the KD should help to develop more reliable markers of efficacy.