Measuring morning melatonin levels with plasma melatonin ELISA kits is a poor choice on two levels

Recently published guidelines for the Journal of Pineal Research stated that "Measuring melatonin using a single time point is not acceptable" and that "reporting only daytime melatonin levels will rarely be acceptable unless there are special circumstances or populations" [1]. In that commentary, it was explained why 24 hour profiles collected under dim light are required to gain an understanding of potential changes in both the Dim Light Melatonin Onset (DLMO) and the total amount of melatonin being produced. Nevertheless papers continue to be published in other journals that compare melatonin levels between groups of human subjects in samples collected at 0800h, 0900h or later.