It is rare that clinicians ordering psychotropic levels must concern themselves with the details of laboratory assay methods, or how the results are reported. For example, knowledge of lithium kinetics has existed for nearly 50 years, and lithium is preferentially administered as a single bedtime dose to minimize the renal dysfunction associated with multiple daily doses, to improve adherence, and to facilitate obtaining levels as 12h troughs in the morning [1–4]. Nearly all commercial laboratories use a standard assay method (ion-selective electrode), and there is limited variation in the laboratory reported therapeutic range: the lower limit is typically 0.5 or 0.6 mEq/l, and the upper limit 1.2 mEq/l, with alerts for levels > 1.2, 1.5 or 1.6 mEq/l [3, 5, 6].