Specifically used by diabetics (7)
I believe the answer is:
insulin
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for insulin that I've seen before include "Protein hormone in the pancreas" , "Hormone controlling sugar supply" , "something to do with the pancreas" , "Hormone secreted by the pancreas" , "Treatment for diabetic" .)