Yes, I have lived with relatives with diabetes and understand that it's quite complex. I don't think anyone with diabetes would suggest that it should be ok to just start taking insulin without a doctor involved, which is (to my understanding) the basic argument for whether a drug should require a prescription or not. You can make a separate argument about whether it should be a longer prescription, or about the failings of a system where seeing a doctor at all is prohibitive for some people, or the fact that the medication is outrageously expensive (which is not directly related to the need for a prescription at all).
Going further, the calculations are rule of thumb and generic and each person has to make adjustments based on intuitions about their metabolism, what they ate, what they plan to eat, what activity they anticipate, and when they last dosed. It's every day, for the rest of their life.
[Source]
Scott Hanselman interviews OpenAPS hacker Dana Lewis:
http://www.hanselminutes.com/514/the-open-artificial-pancrea...