Uh, quick question, while Lou has helpfully already called himself a fucking dumbass for me... how do you forget you're wearing one shoe and one slipper? I guess the natural answer here is because you can't feel your fucking feet go to the goddamn doctor Lou, but seriously. That slipper is clearly looser on the foot than the shoe, which means even if he can't texturally feel the difference it should be obvious that one's sliding around a lot more.
At this point I think he goddamn well knows he desperately need to go to the doctor. I think he knows that he's showing plenty of signs of a raging diabetic... and I think that's why he doesn't want to go, because even though he clearly needs it and it's putting his health at risk, he desperately doesn't want to deal with it just yet. Diabetes is a condition with upkeep costs, that takes actual work. It's not a big onetime hospital bill that he can dodge forever and carry on as normal; it means medication costs, it means injections or a pump, it means that he has to kiss his funtime wants money goodbye because he can't avoid insulin. And when he goes in, he'll also have to face that doctor, who will tell him (however gently) that he's done this to himself.
I legit think this is him trying to just hold off the inevitable, because facing it scares and saddens him. And that's just going to make it all so much worse in the long run.