Here's more information than you probably want about my experience.
I saw a pediatrician from the late 1980s through the 1990s with my last visit just after the turn of the millennium at age 18 for my college physical.
I was lucky to very rarely have to see the doctor for a sick visit. On those occasions, I'd only have to undress to facilitate examination of the part that's sick.
For physicals, though, it was a different story. I'd be weighed and measured in a separate room and only had to take off my shoes for that part. Then the nurse would lead me to an exam room where I'd have to undress. I always had to get down to my underwear, but the way I was told to do it was unique for each nurse.
As far back as I can remember, up to age 13, there was one older nurse who came across as mean but wasn't really. She'd always say it the same way: "Everything off but the underpants." The use of "the" instead of "your" really made the process feel a bit impersonal, and it still gives me chills to this day.
At one of my exams as a teenager, a new younger nurse simply said: "Take off your shirt, and he'll be in shortly." I was surprised, so I had to clarify: "Just my shirt?" She replied: "Well, your shorts and stuff have to come off too." I'm glad I clarified because I would have hated to have done it wrong -- at the time I was very worried about not being good and having the doctor call my mom back to the exam room.
Finally, at my last exam there, another new nurse listed everything she could think of: "Take off any shirts, undershirts, tank tops, t-shirts, socks, pants, shorts, and boxer shorts." I was too embarrassed to get clarification but decided to be brave and leave my boxer shorts on. When the doctor came in, I told him that the nurse told me to take them off, but I wanted to keep them on while I waited. He seemed surprised and said that there's no need to take my boxer shorts off and got right to work examining me in my underwear just like every other visit.