I usually don't get all that pissy about doctors running late. However, there was one time I was really irritated.

I took my wife to the doctor for an appointment. She got the first appointment of the day. We were there 45 minutes early. We waited more than 30 minutes past when the appointment was supposed to start. While we were waiting there, the doctor came in through the waiting room.

It's one thing to be running late because of the normal day to day delays that happen in a medical practice, but if you're actually just running late getting to work, you should call and have your staff let the patients know.