My son was diagnosed at age 18 so I understand totally about trying to figure out how much to step in and how much to take responsibility. As long as he doesn’t mind, I woukd recommend continuing going to his appointments with him, I find this is the best way to know exactly what is going on as the second-hand info I get from him when he does go to appts by himself is not nearly as detailed as I would like IYKWIM.
If you haven’t already done so, when you are at the doctor have him sign a release so that they can give you information, etc. My son’s endocrinologist office would not even let me schedule an appointment for him!
It wouldn’t hurt for him to start calling in his own refills. My son went away to college 6 months after his diagnosis, at first I did all his refills and mailed them to
him but now he mostly care of them himself. He also has ADHD which is not a good combination as he often finds himself running out of things and scrambling at the last minute