What Does Neutering Involve? Female dogs are spayed by removing their womb and ovaries, and male dogs are castrated by removing their testicles. In both cases the operation is performed while the dog is under anaesthetic and strong painkillers are given to combat any pain. Depending on your dog's age, size, and health, he or she will need to stay at your vets for half a day or in some cases overnight. Depending upon the procedure and suture material used, your pet may need stitches removed after a week. The traditional age for neutering is six months although some vets are now recommending neutering from as young as twelve weeks due to additional benefits. Your vet can fully explain the neutering procedures to you and discuss with you the best age at which to neuter your dog.