[joveian]

Good point, that would certainly confuse the situation if there was a 5x variation. Even though they aren't treated the same as drugs there are still quailty standards in the US, although they don't seem to be enforced very well. I try to find suppliers that do better testing. If you have the money for FDA approved stuff you can get ramelteon or tasimelteon these days. But they are quite expensive. Although it looks like the ramelteon patent expires next year and there are a couple of approved generics already so prices should go down quickly next year:

https://www.drugs.com/availability/generic-rozerem.html

I got 1g pure melatonin powder from a now gone supplier that did good quailty testing. It takes me several tries to get something that looks like about .3mg since it is such a tiny amount and I'm sure there is quite a bit of variation, but I'm fairly sure I at least get < .5mg each time.