Low doses of melatonin can be really helpful, especially if people have tried all the "sleep hygiene" steps and that's not working and they don't need a z drug yet.
One of the problems of melatonin is that in some countries it's sold as a supplement not a medication, so the regulation is much less strict.
The dosing varies so much, even in product labelled as 1 mg.
> In this issue of the Journal of Clinical Sleep Medicine, Erland and Saxena systematically analyzed the actual melatonin content (and presence of contaminants) in 31 melatonin supplements purchased from groceries and pharmacies in one city in Canada (before countrywide OTC use of it in Canada was banned). Their findings herald what may also be true in OTC melatonin supplements marketed in the United States. Melatonin content varied from an egregious −83% to +478% of labeled melatonin and 70% had melatonin concentration ≤ 10% of what was claimed. Worse yet, the content of melatonin between lots of the same product varied by as much as 465%.3
> The most variable sample was a chewable tablet (and most likely to be used by children). It contained almost 9 mg of melatonin when it was supposed to contain 1.5 mg and also exhibited the greatest variability between lots (465% difference). The lowest melatonin content was −83% compared to its labeled value in a capsule that also contained lavender, chamomile, and lemon balm. Capsules showed the greatest variability between lots. Liquid supplements surprisingly showed generally high to median stability with low lot-to-lot stability. The least variable products were those that contained the simplest mix of ingredients, generally oral or sublingual tablets with melatonin added to a filler of silica or cellulose derivatives and were the most reproducible. The last disturbing finding was more than a quarter of melatonin products contained serotonin, some at potentially significant doses. Serotonin is a breakdown product of melatonin metabolism but could have medicinal effects and should be taken without oversight. In short, there was no guarantee of the strength or purity of OTC melatonin.
One of the problems of melatonin is that in some countries it's sold as a supplement not a medication, so the regulation is much less strict.
The dosing varies so much, even in product labelled as 1 mg.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5263069/
> In this issue of the Journal of Clinical Sleep Medicine, Erland and Saxena systematically analyzed the actual melatonin content (and presence of contaminants) in 31 melatonin supplements purchased from groceries and pharmacies in one city in Canada (before countrywide OTC use of it in Canada was banned). Their findings herald what may also be true in OTC melatonin supplements marketed in the United States. Melatonin content varied from an egregious −83% to +478% of labeled melatonin and 70% had melatonin concentration ≤ 10% of what was claimed. Worse yet, the content of melatonin between lots of the same product varied by as much as 465%.3
> The most variable sample was a chewable tablet (and most likely to be used by children). It contained almost 9 mg of melatonin when it was supposed to contain 1.5 mg and also exhibited the greatest variability between lots (465% difference). The lowest melatonin content was −83% compared to its labeled value in a capsule that also contained lavender, chamomile, and lemon balm. Capsules showed the greatest variability between lots. Liquid supplements surprisingly showed generally high to median stability with low lot-to-lot stability. The least variable products were those that contained the simplest mix of ingredients, generally oral or sublingual tablets with melatonin added to a filler of silica or cellulose derivatives and were the most reproducible. The last disturbing finding was more than a quarter of melatonin products contained serotonin, some at potentially significant doses. Serotonin is a breakdown product of melatonin metabolism but could have medicinal effects and should be taken without oversight. In short, there was no guarantee of the strength or purity of OTC melatonin.