My MDs differ on whether they refer to themselves as Dr Lastname or Firstnane. I also fluctuate between the two, depending on their age and Th venu in which we met.
If they introduce themselves to me as a Dr Kastnsme, we go with that and they often call me Mrs Lastname. If they call me by my 1st name, they generally ask me to call me by their first name and we generally do that when we are talking face to face.
In conversation with others, whether I refer to them as first name or Dr Lastnane depends on how the others in the audience generally refer to them as.
The same with phds. I generally take my cue on how to address them by how they address me. If they are talking to me by my 1st name, I call them by their 1st name. I inked eould call them Dr when introducing them in a speech where their PhD is listed on s program or if everyone is going by Dr and Other titles (rare). In a clinical setting it is unnecessarily confusing to refer to a PhD as Dr.