So I've been taking 1mg melatonin every night for the past year or so. Been great, sleep great, wake up refreshed.

The past couple of weeks, I've been sleeping great but when I wake up, no feeling of refreshment at all. I'd be exhausted from alarm to bed time.

I've tried adjusting what time I've gone to bed, typical sleep time is 7hrs but I've tried everything from 8 to 6 hours, no difference. Still tired.

So last night, I decided to not take the melatonin.

Slept the same as normal, but woke up feeling good instead of groggy. It's still early in the day, but no tiredness to speak of yet (I'd normally be going for another cup of coffee by now).

Is the melatonin to blame? I don't know the half Life but surely I haven't built up some extraordinarily high sserum levels, right?