lactose intolerance is a very very different thing from diabetes.
Insulin is a fundamental part of keeping you alive, and if you fuck up the balance you can die which is why diabetes is such a big deal.

Lactose intolerance is just the inability to digest a specific kind of sugar, which means bacteria in your digestive system can gorge themselves and give you an absurd amount of gas and other very unpleasant but ultimately not particularly dangerous consequences.