n adolescent shows signs of DSPS, such as frequently getting up late in the morning and catching up on sleep on weekends, it is important to evaluate them using the Dim Light Melatonin Onset (DLMO) test to gauge the extent of the phase shift. Treating DSPS with melatonin, with close monitoring by a physician, improves sleep. For optimal chronobiotic use, melatonin should be taken about three hours before bedtime and it can be effective in DSPS when given for 4 to 6 weeks at 7 PM. Although melatonin is often viewed by parents as “natural” and safe, it should still be considered a hormonal medication. 3 Furthermore, there are limited data on long-term effects of melatonin in children and adolescents. Notably, the effects of melatonin on bones and sexual maturation are not adequately understood. Therefore, a reliably produced melatonin should be used clinically for a short term and not as a long term “supplement”. Is the Use of OTC Melatonin Sold in North America Safe? Melatonin used as a hypnotic agent for the treatment of insomnia is controversial. Melatonin is available as an unregulated OTC supplement often used in children and adolescents in Canada and the United States (US). Erland and Saxena 4 tested 31 OTC melatonin supplements purchased from grocery stores and pharmacies in Guelph, Ontario, Canada, and analyzed their content. The study showed that there is a high variability in melatonin concentrations, ranging from −83% to +478% of the labelled concentration. 4 In addition, serotonin was also detected in 8 of 30 products tested. 4 More recently, Cohen et al. 5 analyzed 25 melatonin gummy products available in the US market. Of these, one product did not contain detectable levels of melatonin, but had 31.3 mg of Cannabidiol (CBD). In the remaining products, the quantity of melatonin ranged from 1.3 mg to 13.1 mg per serving size. In products that contained melatonin, the quantity of melatonin ranged from 74% to 347% of the labeled quantity. Furthermore, the au