“My teenage son is a type 1 diabetic and needs insulin to survive.”
Insulin used to be extracted from cow, sheep, or goat pancreas.
Learning how to do that might be a sell-able skill when the troubles begin. Along with animal husbandry and butchering.
I looked up how to do that. The question is, how to test the strength of the resulting solution, and how to test what dosage they need? From what I found it could, in theory, be delivered orally, which means the level of purification needed isn’t quite so high.