I'd have no trouble arguing that if a person is diabetic and knows he needs insulin, and knows that he'll go into diabetic shock if he doesn't take it, and that person doesn't take his insulin and gets behind the wheel, he's negligent just in doing that, and responsible for any damages caused if he does go into diabetic shock while driving.

Negligence is measured against the standard of a fictional "reasonable person," who is usually quite a bit more careful than real-world people tend to be.  But that fictional "reasonable person" analysis starts with the defendant as he is, and knowing what he knows.

If the insurance company tries to avoid paying for this, in full, get a lawyer, right away.