I call my pdoc when I am experiencing symptoms that aren't being adequately helped with my meds and that I suspect a med adjustment will improve. (I only use him for meds, not therapy.) I simply tell him what is going on, and if he feels a med adjustment can easily be done or something changed/added without needing an appointment, he will do so.

I asked him once about calling after hours because his answering service are kind of like gate-keepers, asking if this is an emergency (I completely understand why they have to do so; some people call for non-emergency reasons which is an abuse of that system.) His reply to me was that I have never contacted him when it wasn't an emergency in his view, and to just tell them it is --- that I have never been one to abuse that privilege, so he will always take calls from me. That was reassuring to me.