There is a lot of misinformation and misunderstandings about how pet microchips work, and sadly, many microchipped pets never make it back home.  One study found that 48% of microchipped dogs and 61% of microchipped cats that ended up in shelters were never returned to their owners (Lord et al. 2009).  The primary reasons were unregistered microchips and incorrect contact information.  If you don't have time to read the full article, use the Table of Contents or check out the orange boxes for the most important information.

What is a Pet Microchip?

A microchip provides  a unique and permanent ID for your pet, which is stored in an electronic chip about the size and shape of a grain of rice.  The microchip is implanted in your pet using a syringe and is usually placed in the upper back between the shoulder blades.  When a microchip scanner is passed over the chip, the unique microchip ID is displayed.  Microchips are available in several different frequencies and may have 9, 10 or 15 digits.  ISO standard (frequency 134.2 kHz) microchips are best and open source microchips (starting with the numbers 900) should be avoided. 

How Pet Microchips Work

A microchip can help you find your pet if they ever go missing or help you prove ownership of a found pet.  They can also help you identify your own pet if they have been missing for an extended period and their appearance may have changed.   Some people believe that microchips can be tracked remotely like a GPS or radio tag, but unfortunately this is not the case. Your pet's microchip does not have a battery and cannot transmit a signal unless a microchip scanner is passed over it.  

The process of reuniting a lost microchipped pet with their owner is somewhat complicated.  First, someone needs to catch your lost pet and bring them to a shelter or vet where they need to be scanned with a microchip scanner much like scanning a bar code at the grocery store.  The microchip scanner should bring up their microchip number. 

This is where things get complicated.  The microchip number by itself doesn’t tell you much as there are numerous microchip companies and registries.  In order to find the owner of the microchipped pet, the vet/shelter needs to find out where the microchip is registered and then contact the registry for the owner’s contact information.  The AAHA Microchip Registry Lookup site is a good resource for looking up microchip registration though it doesn’t contain all microchips.  This site will (hopefully) provide a list of registered locations, and then the vet/shelter will need to contact the listed companies to get the contact information for the registered owner. 

Why Your Pet's Microchips May Not Work

In order for a microchip to work properly, it must be registered and the contact information must be kept up to date.  Unfortunately, the microchip registration process introduces the chance for many errors that may prevent your lost pet from being returned to you.

Possible reasons that a microchip may not work:

• The microchip may not be registered by the owner.  One study found that 42% of microchips were not registered (Lord et al. 2009).
• The shelter or rescue group may have registered the microchip to themselves, but the owner never updated their contact information after adoption. 
• The microchip may have been registered by a prior owner and never updated by the new owner.  Some pets live in multiple homes during their lifetime, so it is not unusual to adopt a pet that already has a microchip.
• Likewise, the same chip may be registered to different owners in different databases.  Transferring a microchip may be difficult depending on the company, so some people just register the microchip with another company after they adopt a pet. 
• The microchip may be registered with an outdated phone or address.  These days it’s not unusual for people to move and change phone numbers multiple times, so this happens quite frequently. 

How to Find the Owner of a Pet with Microchip Issues

If the found pet has an unregistered microchip or one with incomplete or inaccurate information, you may be able to track down the owner with a little detective work of your own.  Check out this article by Lost Dogs of America to learn more.  Or try contacting Microchip Hunters, a volunteer group which provides assistance in tracking down unregistered microchips or ones with out-of-date contact information.

Is Your Pet’s Microchip Registered?

Are you sure that your pet’s microchip is registered, and the contact information is correct?  Don’t wait for them to go missing to try and do this because you need to know their microchip number in order to register the chip.  If you can’t find your microchip records, you may need to bring your pet to a vet or shelter to get them scanned to learn the chip number. 

If you are unsure where or even whether your chip is registered, enter their number into the AAHA Microchip Registry Lookup, which will search multiple registry databases.  If you find that your microchip is registered, make sure that you are able to login to your account and that your contact information is correct. 

Where to Register Your Pet's Microchip

If you find that your pet’s chip is not registered, there are many free and paid microchip registries to choose from.  Just because you have a HomeAgain chip doesn’t mean you need to register with HomeAgain.  Likewise, if you have a 24PetWatch chip, you can register with HomeAgain or other microchip registries.  

Some companies require an initial registration fee and many will also try to get you to sign up for a membership.  Memberships may be helpful (depending on the benefits) but are usually not necessary to keep your chip registered or to update the information.  In my opinion, many microchip companies make the process of registering and updating your information unnecessarily difficult if you don’t pay for their membership plans. 

While there are many microchip registries available, they are not all created equally.  I recommend registering your chip with two companies in case one has a database error, goes out of business or is difficult to reach.  I use HomeAgain, which requires a small fee, and the free 24PetWatch for my pets.  

Be aware that some registries offer much better customer service then others.  Presumably paid services would offer better support, but this may not be the case.  Before registering your pet, visit the site and see how easy it is to report a lost pet or look up a found pet’s microchip.  Try calling and see if you get to talk to live person or if you’re kept on hold for an extended time.  You could also check out online reviews before selecting a company and make sure they are among those listed on the AAHA Microchip Registry Lookup site.  

Are You Sure that Your Pet’s Microchip Works?

In addition to registration errors, there are unfortunately other reasons that your pet’s microchip may not work.  

Mechanical errors: 

• The chip or scanner may be defective. 
• Even functional scanners don’t pick up every microchip.  One study found that scanners detected between 88% - 95% of microchips (Lord et al. 2008).  They also found that some brands of scanners and microchips worked better. 
• A microchip scanner with a low battery may miss picking up an implanted chip.

Biological errors: 

• Most microchips are implanted between the shoulder blades, but occasionally a chip will migrate to another part of the body.  This makes the chip more likely to be missed in a scan. 
• Microchips are more likely to be missed in heavier animals (Lord et al. 2008).

Human errors: 

• The person using the scanner may not scan thoroughly enough and could miss the chip. 
• The scanner being used may not be compatible with the microchip being scanned.  Universal Microchip Scanners will pick up all chip frequencies, but not all scanners are universal.

Have your pet’s microchip scanned periodically to make sure that it still works and hasn’t migrated to another part of their body.  Your pet's annual vet checkup is a good time to do this.