Your last line sums up my hopes as well.
At this moment, I don't think all modern medicine and tech needs to be done away with. Or at least, if it does, it surely wouldn't disappear overnight any more than automobiles, cell phones, or this internet connection we're now using. Many things could likely still be salvaged, scrapped together, repaired, etc., as mass production began to cease.
Synthetic insulin is obviously not something that falls into those categories (use, res-use, cobble together, repair), but the idea that it is here today, gone tomorrow, is unlikely in my view. I realize that my answer is more philosophical than practical, but to me one of the beautiful aspects of anarchy is the notion that there are possibilities for everything currently unimagined in the hierarchical, money-based, separated society. I wish I could see more clearly the path from here to there, but I try to keep in mind it is not a linear one, and that seems to help a little. I've found that believing in anarchy and working toward living it is fraught with contradictions and conflict, and this particular situation you've described is similar in that regard. I suppose those of us who have chosen this view are drawn to and appreciate that conflict in some way, as difficult as it may be.
My wife was a pharmacist in our previous life, so perhaps she has some more tangible ideas than me on the specifics of diabetes...I'll talk to her and respond again later.