Originally Posted by Charcoal
He said they were too small last time so I wasn't sure if there was a set age limit or weight limit before they could be microchipped. He said the needle they use is huge and would hurt them.
If they are small I would agree with your Vet. Tippy and Felicity were 3 months old and microchipped at the shelter before they were released to us. They were "normal" size and whilst Tippy miaowed like she does when vaccinated it didn't unduly alarm her.
Lily is tiny - she was just 3 pounds at 7 months and was microchipped - the needle is big for such a small kitty and she doesn't have much fat on her. She squealed horrendously, it just about broke our hearts. It took the vet 3 attempts and we were about to tell her to leave it and we would have it done when she was spayed and under anaesthetic but she finally got the needle in.
Based on that, if they are small, I would say it is worth doing, but probably better done when they are neutered.