Helping the Lost Get Home: All About Microchipping Pets

It was an early evening in the middle of Summer. I was sitting at my desk at my veterinary hospital writing up some records when one of the assistants approached me and said that one of our regular clients had found a dog running along the side of a busy road, had managed to catch him, and had brought him to us.

Naturally, we were concerned the pup might be injured, especially being found on a road with lots of traffic. The assistant brought him back for me to look at him and he miraculously appeared to be unhurt, though a little muddy.

After determining he was stable and just a little spooked from his sojourn through the urban landscape, we immediately fetched our microchip scanner to check for a registered microchip.

Fortunately, after a second or two scanning over his shoulders, the scanner emitted a “beep” and a fifteen digit number appeared on the screen.

By putting this number into a microchip look-up database, we were able to find which company produced the chip. We were then able to contact the company, and find out who the chip was registered with.

A phone number was provided, and we were able to contact the lost pup’s owners, who as it turns out, had been frantically searching for him for the previous two hours. Thanks to his microchip, we were able to reunite this pup with his family.

But not every pet is so fortunate. HomeAgain, one of several microchip manufacturers, states on their website that without any identification, 90% of pets will not make it back to their homes and families.

A 2009 study published in the Journal of the American Veterinary Medical Association looked at nearly 8000 stray cats and dogs entering shelters between 2007 and 2008. While less than 25% of dogs without microchips were returned to their families, over 50% that did have microchips made it home.

The statistics are even more relevant for cats, with less than 2% making it home without a microchip but almost 40% making it back if they did have one.

How Lost Pets Get Lost

When you drive through your neighborhood, it can be common to see flyers posted on stop signs and telephone poles. “LOST CAT” or “LOST DOG” are fairly common ones to see. Almost as common as ones for yard sales.

But how do pets get lost? The reasons are as numerous as the number of pets who do get lost. According to the American Humane Association, 10 million pets become lost or are stolen every year in the United States.

How did the dog who showed up at my practice get lost? As it turns out, the screen door was left unlocked while the family was at a neighbor’s house–no one could remember who was responsible or how it was overlooked–and he apparently pushed it open himself and two hours later was found a quarter mile away on a very busy street.

Why did he push the door open? No one was there to see it, but he might have seen another dog or a loud noise or other stimulus might have scared him, who knows. Why did he wander so far? A dog’s nose is many times more sensitive than our own and following those smells can be irresistable. Pets who get out may think it great at first, but if spooked by a car horn or other loud noise, they panic, run, and before they know it, are far from home.

The bottom line is that there are so many reasons and variables that can lead to a pet becoming lost and we can’t possibly control them all. What we can do is provide our pets with something that increases their chances of being recovered and returned.

And that something is a microchip.

In this article, we’re going to review what a microchip actually is, the benefits for making sure your pet has one, and a few other considerations, like when the best time is to microchip your pet, and concerns some pet parents may have.

What is a Microchip?

A microchip is a small coated glass cylinder, about the size of a grain of rice, that contains a small electronic chip. Radiowaves at a certain frequency emitted by a special scanner, such as the one at my practice, activates the chip which transmits an identification number.

According to the AVMA, there are a couple of different frequencies used by different microchip manufacturers, but the International Standards Organization (ISO) standard frequency is 134.2 kHz.

ISO microchips are important, because they are an attempt at creating an international standard that allows all standard microchips to be read by any microchip scanner. This is especially important with international travel, which we’ll cover a little later, because a microchip implanted in a dog in the US could be scanned and read by customs in Germany.

How is a Microchip Implanted?

Microchips are typically implanted by an individual trained in where and how to do it. This might be a veterinary professional or a staff member at the local shelter.

A microchip comes packaged inside a syringe. Similar to when any kind of injection is given, like a vaccine or medication, the needle is placed under the skin, usually in the region of the shoulders, the plunger is pushed down, and the microchip is safely seated under the skin.


When is the Best Time to Microchip and Does it Hurt?

The syringe containing the microchip has a needle that is larger than your typical vaccine needle. Some dogs and cats do react to the initial needle poke, while others do not.

For some pets, especially ones who appear to be more sensitive to even the smallest vaccine needle, I will use a topical numbing cream on the skin, as this does reduce anxiety and association of discomfort with being in the veterinary clinic.

Is sedation or anesthesia needed? No, neither is necessary to implant a microchip in an average pet. For pets who have a higher level of fear anxiety and commonly require sedation for vaccines or bloodwork, sedation may be needed to implant a microchip as well. Sedation may also be recommended for a very hyped-up and excited pup, just to ensure the microchip is implanted properly the first time.

Often, we will microchip young dogs and cats while they’re already under anesthesia for spaying or neutering. But if you have already discussed with your veterinarian waiting longer to spay or neuter, as may appropriate with certain breeds of dogs, you may definitely want to consider microchipping sooner. Dogs and cats that still have not been spayed or neutered by the time they reach maturity, are far more likely to attempt roaming behavior to find other dogs or cats of the opposite sex, and are at a higher risk of getting lost.

Your veterinarian will be a good judge of the most appropriate time and method to use to microchip your furry friend, but in general, if your pet is older than 6 or 7 months, you need to consider doing it as soon as possible.

But Aren’t My Dog’s Collar and Tags Enough?

A microchip does not replace a collar and tags, especially the tag providing proof of rabies vaccination, but a collar and tags can’t replace a microchip either. And for one simple reason: a collar and tags can be removed.

According to the American Kennel Club, which has a couple of good articles on pet theft, about 2 million dogs are stolen each year, and only about 10% are ever returned.

A microchip is extremely difficult to remove. While a microchip scanner can localize the region where a microchip resides, its specific location can only be pinpointed using x-rays. A microchip would then have to be surgically removed–not an easy feat for most pet thieves. Only rarely can a microchip be felt through the skin, in some dogs with very thin hair coats and skin. Even then, trying to feel for something as small as a grain of rice is no easy feat either.

For cats, we in the veterinary field generally discourage using identification collars in cats that go outdoors. Because cats have a tendency to jump to very high locations like the tops of fences and tree branches, a collar poses a strangulation risk, even with the quick-release mechanisms many of them now come with. And of course, if your kitty wears a quick-release collar and it comes off, you’ve now lost your only means of identifying her. A microchip poses no such risks and is far more reliable.

What Type of Information Does a Microchip Contain?

Folks may ask this question for a couple different reasons. On one hand, some folks may hope that a simple scan will bring up all sorts of information about their pet, including medical history. Others may be fearful that their own personal information could be stolen through their pet’s microchip.

Essentially, microchips only contain the information that you want them to, which most often is an owner’s name and phone number. This information is also not stored on the chip itself, but in a database associated with the company that manufactures the chip, like HomeAgain, 24PetWatch, BuddyID, and others.

At the most, you can include multiple phone numbers and a home address, but more detailed information, like full medical records, cannot be stored in a typical microchip database.

It’s extremely important to keep microchip information up to date. If a microchip is implanted, but is never registered and no information is provided, it is essentially useless. Likewise, if you adopt a new pet who, say, was surrendered to the shelter and already had a microchip, it’s necessary to update all registration information or the previous owner might be contacted instead of you.

In 2009, the American Animal Hospitals Association created a lookup system called the Universal Pet Microchip Lookup ( whereby a microchip number can be typed into a search window and the company who made it will appear, along with their contact information. If you did adopt a pet who already has a microchip, or if you can’t remember if your pet’s registered information is current, the number can be typed in here so that the company can be contacted and personal information updated.

I’ve Heard About Adverse Events Associated with Microchips, Even Cancer

In 1996, the British Small Animal Veterinary Association started a database to record adverse reactions to microchips. During that period, 4 million animals were microchipped and only 391 adverse events were reported. Of these adverse events, migration of the chip to somewhere other than the original implantation site was the most reported. Most often, migration only means the chip has moved from under the skin of the shoulders to under the skin of an associated limb. But we’re not talking about migration to the heart or other vital areas. Other adverse events, like infection, hair loss, and tumors, were reported in even lower numbers.

According to the AVMA, cancer associated with microchips has been reported in only two dogs and two cats. And in at least one of each, the tumor could not be directly connected to the microchip.

Tumors have also been reported in mice and rats, but these were reported in mice and rats used already for cancer studies and had been genetically modified to be more likely to develop cancer in the first place.

Additional Benefits to Microchips

In addition to the benefits we’ve already talked about that involve recovering a lost pet, there are a couple of other ways microchips can be beneficial.

International Travel

There are many countries, especially in Europe, where implantation of microchips on a pet are a requirement for travel.

As mentioned earlier, when traveling internationally with a pet, it is extremely important to make sure he has an ISO standard microchip. You can tell an ISO chip based on the number, as these chips will always have a 15 digit number with no letters.

Other microchips with shorter letter/number combinations are becoming far less common, but it’s still important to check with your veterinarian to make sure the chip they use is ISO compliant, especially if you plan to travel.

While there are newer scanners that may be able to read multiple frequencies, an ISO-only scanner will be unable to read non-ISO compliant chips and a pet could be considered to be “chipless” by the destination country. If your pet has a chip but it is not a 15 digit number, it is typically recommended to have a new ISO standard chip implanted.

This brings us to the question of whether or not a pet can have more than one microchip. They can in fact, and this raises no additional health risk. The chips also do not interfere with one another or cancel each other out, but it can be helpful to know if more than one chip is present, in case one chip’s registration information is updated and the other’s is not.

Microchip Compatible Doors

Have an indoor/outdoor pet but don’t really like the idea of a thin flap of rubber to keep out raccoons, foxes, and other wild critters?

There are doggie/kitty doors that come with the ability to set it to a microchip frequency. This allows only the dog with the right microchip to be able to exit and re-enter the home through the door. This can also be helpful if there is one pet who is allowed to go outside, like the family dog, but not another, like your cat.

Microchip Compatible Feeders

Have a pet, especially a cat, on a special diet that the other two shouldn’t be eating? Have a kitty who likes to steal the other pets’ food and ends up with a significant weight problem?

There are microchip compatible feeders, like the SureFeed, that only allow the food container to open for a particular microchip. It was the only way one of my office managers was able to get her obese cat to lose weight in a multi-cat household where meal-feeding was not practical for her. Her male cat would sit right behind one of the other cats and try to dart in after she was done, but the accordion-style sliding door was always too fast for him.

These feeders are not inexpensive, especially if you need one for each cat, but if you’ve had it with trying other techniques, these really work well.

Check the Chip!

Microchips are extremely important and beneficial. The bond we share with our pets and that they share with us can be easily broken with a simple accident or mistake. But with a microchip, such unfortunate occurrences can be overcome and that bond can stay intact.

August 15 is National Check the Chip Day. This is a day for pet owners to be aware of the benefits for microchipping if their pet does not have one, but also for keeping a pet’s chip up to date with current information if one is already present.

Some veterinary clinics even offer discounted microchipping on Check the Chip Day. Although microchips typically aren’t very expensive, this can be an additional incentive for pet owners to get their pets microchipped. Make sure to check with your veterinary practice for any offers.

Being able to contact that lost dog’s owners and hear the relief in their voices that their pup was found and okay, was extremely rewarding as a care provider. So if your pup or kitty isn’t microchipped, make sure to talk further with your veterinarian about microchipping and how it is done with your local veterinary clinic.


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Dr. Chris Vanderhoof, DVM, MPH

Chris is a seasoned veterinarian with over 15 years of animal health experience in small animal, large/farm animal, equine, and public health fields.

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