When scientists do preliminary studies on substances to try to find out levels of toxicity, they have developed a number called the LD 50. The LD 50 is the dose that will consistently kill half of the mice that they give the substance to. Well, Melatonin HAS NO LD 50 because no matter what dosage was given to mice, they just simply didn't die!
You're totally fine. It's a completely natural medication and there's been studies where groups take 90mg every night for a year and had zero issues.You'll probably sleep in though.
You're gonna fall asleep forever and the only thing that can wake you will be a kiss from a handsome prince. Sorry