My uncle is diabetic and he will eat a lot and say well i'll just double my insulin. is that healthy? i was just wondering because he acts like he's sick and i wanted to know if this is making it worse.

This : This is not safe. Any changes in his dosage must be under the direction of his doctor. There are several types of insulin, some fast acting, some slow acting that, when used strategically, can normalize blood glucose levels over time. It is never advised to double any dose. He could overdose, resulting in death. If your uncle is acting sick, it is very possible that his tendency to change his own Insulin dosage could be the reason. Take him to the doctor right away, he needs clarification and a treatment regimen that works for him.

This is tough: Change begins from within. What he is doing is not healthy, but tell him that you want him around and just taking more Insulin is definitely not the right answer. He is the one how needs to be willing to change and you can only act as a facilitator but not a fixer. Good luck!