I just reread your post----if he's drinking a lot and losing weight , those are classic feline diabetes symptoms. But again, that website i posted is super helpful and encouraging. And the diet change would address those issues also. :)
Hi-i was researching for my kitty having seizures and saw your post. For kidney disease and seizures its important to remove carbs from the diet and dry food. Its a little more expensive but can be the culprit for both issues. Here's a website that really helped me and it's run by wonderful...