How I make a decision to call a doctor -- first, I compare the problem to the pt's diagnosis (this tells me how serious the problem is usually, ie trouble breathing with CHF) then I see if there is anything already given to me (meds, tx, etc.) that I can do to rectify the situation. If my intervention helps or alleviates the problem I won't call, just leave a note. If intervention fails then I will call.
On medication, it depends if the dose given is unusual or way out of limits. If it is close and it is really late I'll usually give and clarify in morning. If it is way out or early enough (before 11pm) then I'll call. and if the prior nurse missed the dose requirements and left it to me, I'll leave them a note to double check their orders
Checking with your charge nurse is a great idea also as they problably know what the doctor will say. Just try to put the problem in context of severity and don't take the doctor yelling personally. You are the one "there" if you feel it is important, then it is important.
Good luck to you,