Going to a adolescent medicine physician. What to expect? Mom allowed in the room?

Initially. A good adolescent medicine physician (and this goes for peds and fam med docs) will try to foster communication between the parent and teen. How they do this depends on each doctor's style. Some will meet with both parent and teen together, then ask the parent to leave to have a one-on-one. Depending on state laws, a teen may be able to see the doc without their parent present.