You did the responsible thing and made sure your pet was microchipped. Either your vet did it or your pet came that way from the shelter or rescue group. You figured that your dog or cat is protected if he ever wanders away ... and there's a good chance you're right.

But did you ever register the microchip? And if you moved or changed phone numbers, did you make sure to update that information in the registry?

Here's what you need to know about microchips and how to make sure your information is up to date.

What is a microchip?

A microchip is a tiny, electronic chip or transponder about the size as a grain of rice that's implanted between your pet's shoulder blades. It's inserted under the skin using a needle just a little larger than those used for regular injections. A microchip contains an identification number that can be read when a scanner is passed over the area where it's placed. It doesn't work as a GPS tool and can't track your pet if your pet gets lost, points out the American Veterinary Medical Association (AVMA).

How is a microchip registered?

When a shelter, rescue group or vet microchips a pet for you, you'll have to register the microchip information for your pet with your contact information. To do so, visit the website or call the phone number for the company that supplied your pet's microchip. There are various brands such as 24PetWatch, HomeAgain and PetLink. Your vet or the shelter will give you the company's name. Then you'll register your pet, typically supplying your name, address and several contact phone numbers, as well as your pet's name and sometimes a photograph.

You also may want to enter your animals in the universal and free Found Animals registry. It's part of the Found Animals Foundation, a nonprofit that works to help more pets stay in their homes.

cat being scanned for a microchip A scanner reads a cat's microchip information, including registry name and ID number. (Photo: Ivonne Wierink/Shutterstock)

How does a microchip work?

If your pet gets lost and ends up at a shelter or veterinarian's office, he hopefully will be scanned for a chip. The scanner will show the contact number and identification number for that particular brand of chip. They can then call the company to find your information and help reunite you with your pet.

How do you update your microchip information?

When you move or change phone numbers, you update your contact information with your pet's chip registry. (Just like you let your aunt know you've moved, let the pet chip registry know, too.) If you don't and your pet gets lost, someone might scan your pet's microchip and be unable to track you down.

To update your information, simply log in or call the company and put in your new contact details. If you don't remember the manufacturer or your pet's microchip number, do a little detective work. If you got your pet through a shelter or rescue group, call them and ask. Many places keep the information on file.

The American Animal Hospital Association (AAHA) has a pet microchip lookup tool if you know the number but not the manufacturer. You can also take your pet to your veterinarian to be scanned and they will be able to give you the manufacturer and microchip number. You may be charged a fee to update the information.

Do chips last forever?

Microchips are designed to work for 25 years, according to the Humane Society of the United States. But there are some problems that can cause microchips to fail or not register when scanned.

The AVMA points out that, as with nearly anything, microchips aren't foolproof. Occasionally, microchips can just stop functioning or a scanner can have problems when trying to read a microchip. It can also be human error when trying to scan a pet. Or an animal may squirm so much during scanning that it causes difficulty in reading the chip.

Other issues can interfere with detection of a microchip including long or matted hair near the implantation site, excessive fat deposits in the implantation region or a collar with a lot of metal.

dog with ID tags Even with a microchip, your dog should still wear a collar with an ID tag. (Photo: SGerace/Shutterstock)

Do I still need a collar and ID tag for my pet?

It may be tempting to forget about your pet's name tag if he has a microchip. But it's much quicker for someone to read a lost pet's tag to track down an owner, as long as the information is up to date. But if your pet's collar and tags are lost or he slips out the door without them, then a microchip might be the only way he finds his way home safely.

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.

Have you checked your pet's microchip lately?
Making sure microchip info is up to date can help a lost pet make it home safely.