Line all subjects, there's a lot of cat misinformation online. Diane K. writes:
Diane, we assure you that the benefits of having your feline friend microchipped far outweigh the potential hazards. First off, let's explain what exactly a microchip is. They're tiny devices inside glass capsules that are about the size of a grain of rice. The capsule is implanted under the cat's skin by your veterinarian, usually between her shoulder blades. A hypodermic needle is used and no anesthetic is required. The "chip" gives off no data signal at all, but can be read by a device to reveal its code number. That number can then be traced back to you, the cat's guardian. Simple, right? Well, not always.
The biggest problem with the current system is that there is no unifying standard for the chips. That means that you need a reader that can identify and read your particular brand of chip. Add in proprietary databases and you have a real mess, but it's getting better. The best choice as of this writing is to follow your veterinarian's recommendations. But once the doc has implanted the chip, there's still work for you to do. You have to register the chip with the device manufacturer. That can be done via info you should obtain from your vet at the time of the implant and will usually come with a fee.
You'll also want to register your pet's chip number with the Found Animals Registry. They're a non-profit, and their mission is to bridge the gap between all the different chip and reader manufacturers out there. Their service is completely free of charge and they allow you to list a main contact (you), a secondary contact, and a veterinarian.
As to those potential hazards that we alluded to, there aren't many. The American Veterinary Medical Association reports:
So, don't worry, Diane. Chipping a cat is a painless way to increase the odds that your cat will be returned to you if he or she gets lost. We wish you all the best!