I suspect the dosage and absorption isn't fully understood yet or very individual. For me some 2mg pills work fine and other 3mg pills don't; currently I use 4mg time-release and it's mostly fine. 1 mg is definitely not enough for me.
I would be groggy a few hours after taking the pill but not in the morning.
Since they're not regulated as medication, melatonin pills have no guarantees about actual melatonin content. In studies, the vast majority of supplement labels are inaccurate.
I would be groggy a few hours after taking the pill but not in the morning.