in ‧ su ‧ lin /ˈɪnsjələn, ˈɪnsjʊlən $ ˈɪnsə-/ BrE AmE noun [uncountable]
[ Date: 1900-2000 ; Language: Latin ; Origin: insula ( ⇨ ↑ insular ); because insulin is made by body organs called the "islets of Langerhans" ]
a substance produced naturally by your body which allows sugar to be used for energy:
diabetic patients requiring insulin