Pet Microchips – How They Work

The technology of a pet microchip is simple and safe. The implantation process is quick, inexpensive, essentially painless, and virtually stress-free for pets and pet parents.

Pet Microchips

No bigger than a grain of rice, a pet microchip is a radio-frequency identification transponder made up of just a few components encased within a slender capsule of bioglass, which is used extensively for implants in both humans and animals. Some animal microchips have anti-migration features to ensure capsules stay in place by bonding with the tissue under the animal’s skin.

  • A microchip’s sole function is to store a unique ID number that is used to retrieve a pet parent’s contact information—it differs from a Global Positioning System, which is used for tracking, and requires a power source such as a battery.
  • When a microchip scanner is passed over the skin of a microchipped pet, the implanted microchip emits an RF (radio frequency) signal. The scanner reads the microchip’s unique ID code. The microchip registry is called, and the registry company uses the ID number to retrieve the pet parent’s contact information from the pet recovery database.
  • Most animal shelters and veterinary hospitals in the U.S. have global scanners that read pet microchips from most manufacturers.

Microchips have different frequencies.

Microchips are passive devices, which means they have no internal energy source. They stay dormant until they are activated by a scanner. In the U.S., several different microchip frequencies have been used for pet microchips:

  • The 125kHz chip – until recently, this was the most common frequency in the U.S., and can be read by most scanners in the U.S.
  • The 134kHz chip – was introduced to the U.S. in 2004. This microchip is defined by specifications developed by the International Standards Organization or commonly known as ISO. The microchip ID code format for this chip is defined as a 15-digit numeric code that uses 0-9, where the first three digits represent a country code or a manufacturer's code. This frequently is considered the “global standard” for pet microchips, as it is used by the rest of the pet microchipping world.
  • The 128 kHz chip – introduced in 2007, can be read by many scanners, but not all.

Does the frequency matter? Yes and no.

  • Virtually all shelters and veterinary clinics have scanners. It is estimated that by early 2008, there were already over 70,000 “universal scanners” in the U.S.—scanners that read all frequencies of microchips ever sold here, including the new ISO standard.
  • Many leaders in animal health recommend the new ISO standard, including American Veterinary Medical Association and the American Animal Hospital Association.
  • If you travel outside of the United States with your pet, it is likely that your pet will need a microchip to enter the foreign country. If so, have your pet implanted with an ISO chip, since most countries outside the United States use the ISO standard and their scanners will not read the other frequencies. If your microchipping pet has already been implanted with a different frequency, some countries will allow you to bring your pet as long as you bring a microchip scanner with you that can read the ID number.
  • Do not microchip your pet again, as multiple microchips can interfere with accurate readings. You should ask your veterinarian which microchip frequency their clinic recommends.


Pet Microchips - How They Work

How are microchips implanted?

  • Pet microchips are implanted by a veterinarian through a quick injection, like a routine vaccination.
  • The site of implantation varies by animal.
    • In the U.S, cat, and dog microchipping is typically injected along the dorsal midline, just between the shoulder blades.
    • Horses are injected along the left side of the neck, about an inch below the mane and midway between the poll and the withers.
    • Birds, which lack the bulk of most animals, receive the implant in their breast muscles.
  • The animal-care professional should scan for existing microchips prior to implanting a new one—this step takes 10 to 30 seconds.
  • No anesthetic is required. The pet’s reaction will be consistent with that of a vaccination injection. The implant procedure is essentially painless.
  • Your pet’s skin is desensitized by a simple pinch that pulls the skin upwards until taut.
  • The animal-care professional inserts the needle.
  • A final pinch ensures the microchip stays in place as the needle is withdrawn.
  • Your veterinarian or animal shelter personnel can help you complete the microchip registration forms immediately following implantation.
  • You and your pet go home and relax together. Avoid rigorous exercise or activity with your pet for 24 hours, in order to give the anti-migration coating on the microchip a chance to bond to your pet’s skin, so the microchip remains where it was implanted.

Will it hurt my pet when he gets the microchip implanted?

It won’t hurt any more than a routine vaccination – having a microchip implanted doesn’t even require anesthetic. The procedure is performed at your veterinarian’s office and is simple and similar to administering a vaccine or a routine shot.

The microchip comes preloaded in a sterile applicator and is injected under the loose skin between the shoulder blades. The process takes only a few seconds, and your pet will not react any more than he would to a vaccination.

Will a microchip tell me my pet’s location?

Pet microchips are not tracking devices and do not work like global positioning devices (GPS). They are radio-frequency identification (RFID) implants that provide permanent ID for your pet. Because they use RFID technology, microchips do not require a power source like a GPS. When a microchip scanner is passed over the pet, the microchip gets enough power from the scanner to transmit the microchip’s ID number. Since there’s no battery and no moving parts, there’s nothing to keep charged, wear out, or replace. The microchip will last your pet’s lifetime.

Why does my pet need a microchip when he already wears a collar with tags?

All pets should wear collar tags imprinted with their name and the phone number of their pet parent, but only a microchip provides permanent ID that cannot fall off, be removed, or become impossible to read.

How much does it cost to microchip my pet?

The average cost to have a microchip implanted by a veterinarian is around $45, which is a one–time fee and often includes registration in a pet recovery database.

If your pet was adopted from a shelter or purchased from a breeder, your pet may already have a microchip. Consult your pet adoption paperwork, or have your pet scanned for a microchip at your next vet visit to reveal the unique microchip ID number and register it.

Isn’t microchipping only for dogs?

Both cats and dogs need to be microchipped.

Cats often do not wear collars, and may not have any other form of ID. A recent study showed that less than 2% of cats without microchips were returned home. However, if a cat is microchipped, the return-to-owner rate is 20 times higher than if the cat was not microchipped.

Can anyone with a scanner access my contact information from the chip?

Microchips carry only a unique identification number. If your pet gets lost and is taken to a vet clinic or animal shelter, your pet will be scanned for a microchip to reveal his unique ID number. That number will be called into the pet recovery service, and you will be contacted using the contact information on file with your pet’s microchip. **It is vital to keep your contact information up to date so that you can be reached.

How many times do I need to microchip my pet?

A microchip will normally last the lifetime of your pet because it is composed of biocompatible materials that will not degenerate over time.

The HomeAgain® microchip has the Bio-Bond™ patented anti–migration feature to help ensure the chip stays where it’s implanted. Also, since microchips require no power source and have no moving parts, there’s nothing that can wear out and need to be replaced. Pet parents can also check to make sure their pet’s microchip is still working by asking a vet to scan it during their pet’s next checkup.

My pet has a microchip. Is that all I need to protect him if he gets lost?

A microchip is only the first step! You must register your pet’s microchip to give your pet the best protection.

Register your pet’s microchip in a national pet recovery database such as HomeAgain with your contact information, so you can be contacted when your lost pet is found. Also, remember to keep your contact information up to date whenever you move or change phone numbers.


You and your pet belong together. Your cat or dog’s microchip implant gives your pet the best chance of returning home to you if lost. However, a microchip must be registered along with your current contact information in order to identify you as your pet’s parent and contact you. Remember as long as there are pets, even those belonging to the most responsible parents, they will go missing.