Melatonin for a healthy rhythm.

According to a scientific review from 2016, the short-term use of melatonin is considered safe (except for pregnant or breastfeeding women, due to a lack of studies there). Long-term melatonin supplementation for children or adolescents requires further investigation. When in doubt, please inform yourself about potential side effects and consult a doctor to make an informed decision. 

If you do decide to take melatonin, there are two things I would like you to know: 

• For sleep, many people take melatonin about 1.5 hours before bedtime. This is fair to help with sleep but will have little effect on your circadian rhythm. If you want to advance your rhythm, a study has shown that melatonin is most potent when taken much earlier. When 0.5 mg of melatonin was used, intake timing for maximal effect was 3.3 h before the natural onset of melatonin, which translates to 5 h before habitual bedtime. 
• Above 0.5 mg, a greater melatonin dose does not seem to yield greater circadian phase shifts. In the aforementioned study, 3 mg of melatonin led to the same average circadian phase advance (1.5 hours) as 0.5 mg. The difference was that the 3 mg supplement had to be taken even earlier for maximum effect, about 7 hours before bedtime.