For the person who seems to be incensed at this, I don't mean that I'll actually grind up horse pancreases unless those are the only ones that I can find. I think that pig pancreases can also be used, but I haven't looked into it much.
Partner actually did a bunch of lab work on this stuff as an intern in highschool with his dad who was doing diabetes research. It can be done with minimal lab equipment. You could replicate injectable insulin in a survival scenario assuming all glass and metal and electronics haven't been stolen by aliens.