What do you mean? Am I just dehydrated when I feel overslept, or oversleeping causes dehydration? The latter makes little sense to me, but I'm asking for clarification because this issue happens to me quite often.

> oversleeping causes dehydration? The latter makes little sense to me

Well, when you're awake you will get thirsty and drink if you overheat. If you're asleep you won't.

both. the longer you are asleep the more dehydrated you are, exacerbating grogginess.