Kittens weighing at least 2.5 – 3 lbs can be fixed and get their rabies shot. Referred to as pediatric or juvenile spay/neuter, the procedure is performed on cats as young as six to eight weeks old, and up to six months, though the weight minimum is usually required.
Kitten Development Guide
Less than one week old: Kittens eyes are shut and their ears are folded against their head. They are not able to walk but do purr and make tiny squeaking noises. You may still see their umbilical cords.
One to two weeks old: Their eyes and ears will start to open and they will begin crawling.
Three weeks old: You will see their ears and eyes fully open and baby teeth starting to come in. They will also be able learning to walk and responding to their environment.
Four to five weeks: Kittens will be fully active at this point and may start weaning from their mothers.
Eight weeks old: They will look like miniature versions of adult cats, with longer legs and adult fur coming in. If they meet the minimum weight requirement, they are ready for spay/neuter and a rabies vaccine. If they are to be adopted, this is the best age to start socializing them to humans.