As I said before, I have not had a problem, and I do not travel with a doctor's note.
DCL did have my medical form before the cruise. All my other scripts are in precription bottles. DCL didn't give my bag a second look. (separate bag carrying all my meds) Actually the only thing they gave a second look was my folding canes and that was only because they were folded and appeared similar to guns. Once shown to the inspectors we were quickly on our way.
In 30 some years of using insulin and travelling all over no one has ever questioned my having insulin and syringes or asked for a doctors note.