Why does my melatonin help me sleep some nights and not others? im taking 5 mg time released. i take nothing else.

Possibilities: A few possibilities. First, there may not be same amount of melatonin in each time-released capsule. True but herbals are not regulared in the us. Also melatonin is inactivated by light so when you are on computer/television at night, may not work as much as if you were, say, reading. Also timing is important, taken after body temperature core min, might not help at all!