As long as you aren't in the business of taking people's blood, we shan't have a problem. That is what you meant, then. I wondered if you had had to defend yourself from some crazed doctor. Defending a thesis is much more sensible.
Well, where I am from, calling someone by his first name is something you wouldn't do unless he was very young, you were exceptionally close, or you were trying to be rude and dismissive.