Microchip Fact Sheet

The Microchip World: Recent Advances and Options for Shelters and Veterinarians

Linda K. Lord, DVM, PhD, Assistant Professor
Department of Veterinary Preventive Medicine, The Ohio State University


Currently a national standard for microchip identification of companion animals does not exist in the United States (U.S.). Throughout much of the world, the International Organization for Standardization (ISO) standard of 134.2 kHz for radio frequency identification devices (RFID) has been adopted and implemented as the preferred or sole RFID technology for companion animals.1-2 This standard has been endorsed by groups such as the American Veterinary Medical Association, the American Animal Hospital Association, the Humane Society of the United States, the American Society for the Prevention of Cruelty to Animals, and the Society of Animal Welfare Administrators, as well as the National Standards Institute (ANSI). In the U.S., however, the non-ISO 125 kHz microchip is still predominantly utilized.

With the majority of the current U.S. microchips functioning at 125 kHz, there are now 3 distinct frequencies in the U.S. market. In the last 2 years the 134.2 kHz ISO microchip as well as the 128 kHz microchip have been introduced into the U.S. In addition, the 125 kHz microchips can be encrypted, meaning they are read with a different communication protocol than the 125 kHz unencrypted microchips. With the introduction of multiple microchips operating at different frequencies as well as different communication protocols (i.e., encrypted vs. unencrypted), several universal scanners that can read or detect all three frequencies have been introduced. A functional radio frequency identification system is based on three core components, the microchip, a reader and a database that links the chip number to the pet owner. Based on global dynamics and the introduction of the 134.2 kHz ISO microchip in the U.S., many believe a move towards national adoption and implementation of the ISO standard is inevitable. However, regardless of whether this occurs or not, a robust, functional universal scanner is of paramount importance in bridging the current technological incompatibility that exists within the U.S.

There has been growing concern that the new universal scanners may not sufficiently or rapidly detect the presence of some microchips. In order to address this concern, the authors developed two studies to test the sensitivity of some of the scanners in the market for reading various brands of microchips operating at the different frequencies both in experimental and field conditions. Additional detail can be found in the published studies.3-4 Findings for the field study conducted in the shelter environment are presented here.

Microchip Scanner Sensitivity

The microchips were chosen for testing that represented the major manufacturers and frequencies in the U.S. The microchips evaluated were the Avid FriendChip microchip (encrypted 125 kHz), HomeAgain (Digital Angel) microchip (unencrypted 125 kHz), 24PetWatch (Allflex) microchip (unencrypted 125 kHz), American Kennel Club-Companion Animal Recovery (AKC-CAR) ID System (Trovan) microchip (128 kHz), Bayer ResQ (Datamars) microchip (134.2 kHz), and the HomeAgain (Digital Angel) microchip (134.2 kHz). For the 4 scanners included in the studies, the read (detect presence of microchip and read/display the number) and detection (detect presence of microchip only) capabilities are given in Table 1.

In the shelter study, at each of the 6 shelters, 440 dogs and cats were implanted with a microchip and 220 animals were used as controls. Each of the 6 shelters tested a different microchip brand. The people that were scanning in the study were blinded as to whether an animal had a microchip and the order in which control or implanted animals were scanned was randomly assigned. In addition, the scanners were randomly assigned to different people for different animals to avoid any operator bias in the scanning process. All participants were trained by a study coordinator to follow proper scanning technique as described in Table 2.

The sensitivity (sensitivity defined as the percentage of successful scans (read or detected) for each scanner for each microchip) for each of the scanners for each microchip are given in Table 3.

Maximizing the Success of Detecting a Microchip

Although no single scanner performs with 100% sensitivity, several key points can be made to optimize the effectiveness of the microchip scanning process:

• Use proper scanning technique and make sure all personnel are trained
• Scan an animal more than once. In the shelter environment, animals should be scanned at intake, at medical processing, before euthanasia, and before adoption
• Have a regular battery change schedule and use a high quality battery brand such as Energizer
• Avoid interference by scanning away from computers, metal tables and fluorescent lighting. Remove any metal collars prior to scanning

Making the Registration Process Successful

A microchip without a current registration is an ineffective method for pet reunification. It is important that both shelters and veterinarians recognize and support the microchip registration process to maximize the likelihood of reuniting pets with their families. Several steps that shelters and veterinarians can take to help with microchip registration include:

• NEVER separate the microchip implantation process from the registration process with a national microchip registry. Whether or not you are a shelter or a veterinarian, you need to bundle microchip registration with microchip implantation. If at all possible, collect the information and process the registration for the client or adopter to make sure this step is performed.
• Consider contacting more than one registry if the manufacturer’s registry doesn’t have current registration information for a microchip. Microchips are registered with multiple registries and this may help to find the owner. Use the new AAHA microchip lookup tool to find out what registry has the information for the microchip. It is available at http://www.petmicrochiplookup.org.
• If in a shelter environment, always contact the microchip registry for owner surrender animals as well as stray animals. Instances occur where the person surrendering the animal is not the original owner and the original owner still wants to reclaim their lost pet.
• If in a veterinary office, scan animals at the time of the annual wellness examination. Make sure the microchip is still functioning and remind owners to update their information.

In our study5 of 53 shelters who recorded information on animals entering a shelter with a microchip we found that:

• 73% of owners of stray dogs and cats were found (74% for dogs and 63.5% for cats).
• 74% of the owners actually wanted their animals back (76% for dogs and 61% for cats).
• The median return to owner rates for the shelters were 2.4 times higher for dogs with a microchip than all stray dogs (52.2% vs. 21.9%) and 21.4 times higher for cats with a microchip than all stray cats (38.5% vs. 1.8%).
• The main reasons that owners weren’t found included incorrect or disconnected phone numbers (35.4 percent), owners’ failure to return phone calls or respond to letters (24.3 percent), unregistered microchips (9.8 percent) or microchips registered in a database that differed from the manufacturer (17.2 percent).

The Total Identification Package

Microchipping alone does not constitute a total identification package. To help maximize the likelihood of successful pet reunification, remember these points:

• Visual identification is the easiest method for pet reunification. Consider sending home collars and custom identification tags with adopters, placing a tag engraving machine in your lobby, and offering tags at any microchip clinics. Veterinarians can discuss visual identification with clients during the annual wellness examination.
• Educate your adopters and clients on the importance of pet identification and what to do if an animal becomes lost. Helpful brochures are available for this education.6
• Offer microchipping during puppy/kitten visits, wellness examinations, boarding and elective procedures such as dentals and spay/neuter surgery.
• Microchipping is a win-win-win for the veterinarian or shelter, the owner and the pet. It is a community service and should be considered a best practice.


1. International Organization for Standardization (ISO). ISO 11784 - Radio-frequency identification of animals – Code structure. Second edition. 1996-08-15.
2. International Organization for Standardization (ISO). ISO 11785 - Radio-frequency identification of animals – Technical concept. First edition. 1996-10-15.
3. Lord, LK, Pennell, ML, Ingwersen,W, Fisher, RA, Workman, JD. In vitro sensitivity of commercial scanners to microchips of various frequencies. Journal of the American Veterinary Medical Association. 2008 Dec 1;233(11):1723-28.
4. Lord, LK, Pennell, ML, Ingwersen,W, Fisher, RA. Sensitivity of commercial scanners to microchips of various frequencies implanted in dogs and cats. Journal of the American Veterinary Medical Association. 2008 Dec 1;233(11):1729-35.
5. Lord, LK, Ingwersen, W, Gray, JL, Wintz, DJ. Characterization of animals with microchips entering animal shelters. Journal of the American Veterinary Medical Association. 2009 Jul 15;235(2):160-7.
6. “Plan for a Happy Reunion” pet identification brochure. Available at: http://vet.osu.edu/brochures.

Other Resources


  1. Objectives and Key Elements Needed for Effective Electronic ID

  2. Backgrounder

  3. Frequently asked questions

WSAVA - Microchip Identification Guidelines

AAHA Training

AAHA Microchip Lookup Tool

OSU Brochure

Study Support

The microchip studies3,4 were funded by (in alphabetical order) American Animal Hospital Association, American Kennel Club Companion Animal Recovery, American Society of Veterinary Medical Association Executives, Bayer HealthCare LLC, Schering-Plough Home-Again LLC, and the Society of Animal Welfare Administrators.