Sucralose, Sold as Splenda, is a chemically alterered sugar. The alteration prevents it's being recognised and metabolised by the body. However, it is still technically a member of the sugar family.
It doesn't affect BG unless you have the powder, which is bulked out with maltodextrin, when the active sugar effect is small. The good thing about Splenda is that it's stable during cooking, so you can bake with it and it won't change its flavour. All the info about it is on the carton.
If you look it up on the web, you'll find loads of websites making a fuss about the chlorine in the molecule. This is chemically bound and not available as gaseous chlorine. I have never found any evidence against Splenda, but there's loads of unscientific prejudice.
Does that answer?