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While spaying is traditionally recommended for kitties between 4 and 6 months of age, spaying as young as 8 weeks old is considered safe, according to Cat Channel. Many animal shelters actually spay kitties prior to adopting them out at this age.
Kittens can be spayed or neutered once they're eight weeks of age, healthy and two pounds in weight. Sadly a lot of vets - and shelters - are behind the times and wait until the animals are six months old.