How to not accidentally kill a diabetic?

Hey! I’ve moved up to uni this year and one thing I really love to do is bake for my friends. One of them is a type one diabetic and I want to bake things that he can eat, without his sugars going crazy, so he isn’t left out. I’ve looked into it and I know that carbs are just as important as sugars for glucose levels and was wondering if cheesecake could be the way to go? I just don’t know if I should factor in substitutes when it comes to things like the sugar and flour? I’ve seen some conflicting information on when to substitute and when, I was just curious about what others thought

Thank you!