Dog Microchips, GPS Trackers and ID Tags

How Dog Microchips Work

A microchip is a tiny radio chip sealed in a glass or plastic capsule about the size of a grain of rice.^1,2 It has no battery. When a scanner passes over it, the scanner powers the chip, which sends back its ID number.^1,14 Key points:^2,1,4

• It holds only a number, usually 9, 10 or 15 digits. It doesn't store your name, address or medical records.
• The number is linked to you only through a registry, a database run by the chip company or another service.
• The international standard is the ISO chip (134.2 kHz, 15 digits), which the AVMA supports. Some older US chips use other frequencies. Universal scanners are designed to read the common types, but no scanner finds every chip every time, and some US scanners miss chips that start with 1 or 8.^15,4,16
• It can't track your dog. It only works when someone finds your dog and scans it.^2,7
• It's designed to last a lifetime, since there's no battery to run out.^14,17

Getting Your Dog Microchipped: Cost, Pain and Age

Your vet injects the chip under the loose skin between the shoulder blades with a preloaded needle. It takes a few seconds and needs no sedation or anesthesia.^2,11

• Does it hurt? It's a quick pinch, similar to a vaccine, though the needle is slightly larger. Some dogs flinch or yelp briefly, and most go straight back to normal.^2,1,17 Many owners have it done while their dog is under anesthesia for spaying or neutering.^2,17
• Cost: usually about $25 to $50, often including registration, and sometimes less at shelter or clinic events.²
• Age: most puppies can be chipped by 8 weeks. Very small toy-breed puppies may do better at 3 to 4 months.⁷ Have a vet or trained professional place the chip.^18,19

Registering and Updating Your Dog's Microchip

A chip without current registration "is an ineffective method for pet reunification," says the lead author of the 53-shelter study.⁴ In that study, owners couldn't be found for about 1 in 4 chipped stray dogs. Wrong or disconnected phone numbers were the most common reason.⁶ To keep your dog's chip working:^8,2,3,20

1. Find the chip number on your vet, breeder or adoption paperwork, or ask your vet to scan your dog.
2. Enter the number in the AAHA Microchip Registry Lookup (petmicrochiplookup.org) to see which registry holds it. The tool doesn't show owner details and can't update them.
3. Contact that registry to register or update your details. Some charge a small fee; others are free.
4. If you adopt a dog, get the chip number and registry from the shelter or previous owner and transfer it to your name.
5. If your dog goes missing, ask the registry to flag the chip as lost.

Microchip Side Effects and Risks

Problems are uncommon.^2,21 In the UK, a government reporting scheme received 1,420 reports (84% in dogs) between April 2014 and December 2015, in a country of about 8.5 million dogs and 7.5 million cats. After review, these included 302 true migrations, 56 true chip failures and 61 reactions.²¹

• Migration: the chip moves away from where it was placed, or occasionally works its way out soon after placement. This is the most common reason a chip can't be found, and why vets scan the whole body.^22,2
• Chip failure: rare. If a chip can't be read, a second one can be placed.^21,22
• Swelling or infection at the site, usually minor^2,23
• Spinal injury: a few cases where the chip went into the spinal canal, mostly in very small puppies, with weakness right after the injection^24,19
• Tumors: only a handful of case reports in dogs, against many millions of chips. A link hasn't been proven.^25,26,27,22

You may be able to feel the chip under the skin in small or short-haired dogs. This is normal.² See your vet if you notice a lump that grows, swelling or soreness at the site, or weakness after chipping.^22,24

ID Tags and Collars

A tag is the fastest way for a neighbor to call you, without needing a scanner.^9,2 Use a tag even if your dog is chipped. Chips "should not replace ID tags but rather complement them."²

• What to put on it: your cell phone number first, a second number if possible, and your dog's name and town. Adding "I'm microchipped" and the registry's phone number can help.^9,3
• Choose flat tags. Slide-on or riveted tags don't dangle, wear out or catch as easily as hanging tags.^9,28
• Check tags every couple of months and replace worn ones. Keep the rabies and license tags on too; the numbers can be traced to you.^9,29
• Collar safety: collars and dangling tags can snag on crates, fences and other dogs' jaws. Take the collar off in the crate and during rough play, or use a breakaway collar that releases under pressure. The microchip covers the time the collar is off.^28,30 Fit it snugly, with room to slide a finger or thumb underneath but not your whole hand, and recheck the fit when your dog lies down.²⁸

GPS Trackers and Bluetooth Tags

A GPS tracker clips to the collar and shows your dog's location on your phone. Most combine GPS with a cellular connection, so they need charging and usually a monthly subscription.³¹ Many let you set a "safe zone" and alert you when your dog leaves it.^31,32

Sources: AAHA, Consumer Reports and CHOICE.^2,31,33

• GPS limits: most trackers need cellular coverage, so they may lose your dog in remote areas without cell service. More frequent location updates drain the battery faster, and trackers can come off with the collar.^31,34,35 Trackers without a cellular plan avoid fees but track far less well.³¹
• Bluetooth tags are made for keys and bags. Their own range is short, often much less than claimed. Beyond that, they rely on passing phones that run the same maker's app, so they may not help where few such phones pass by.³³

A tracker adds the most for dogs that bolt, escape or roam off leash, because it lets you search for your dog instead of waiting for someone to find and scan it. Keep the chip and tag too.^31,2

What to Do if Your Dog Is Lost

1. Search right away, starting nearby, several times a day and at night. Most lost dogs are found close to home. Put familiar-smelling items outside.^12,20,29
2. Call your microchip registry to report your dog lost and confirm your details.²⁰
3. Contact every shelter, animal control office and vet clinic in your area and neighboring ones. Visit shelters in person every day or two, because photos can be misleading.^3,29
4. Post online on local lost-pet pages and neighborhood apps, and put up flyers. Use a clear photo, where and when your dog was last seen, and two phone numbers. Leave out one identifying detail to screen out scams.^3,20
5. Keep going. Keep looking and checking shelters for at least a few months.^3,29

What to Do if You Find a Lost Dog

1. Approach calmly and carefully. Call animal control if the dog seems aggressive or badly hurt.^36,29
2. Check for tags and call the number.³⁶
3. Have the dog scanned for a microchip at any vet clinic, shelter or animal control office. If there's a chip, the AAHA lookup tool shows which registry to contact.^36,8
4. Report the dog to local shelters and animal control, and post a photo online and on flyers.^36,29
5. Ask anyone who claims the dog for proof, such as photos or unique markings. Follow your local rules on how long to hold a found dog.³⁶

Microchips, Laws and Travel

• Entering the US (as of 2026): since August 1, 2024, all dogs entering or returning to the US must be at least 6 months old, have a microchip that a universal scanner can read (the CDC asks for an ISO-compatible chip) and have a CDC Dog Import Form receipt. If your dog needs a rabies vaccination for entry, for example after time in a high-risk country, the chip must be implanted before or on the same day as that vaccination. Rules differ by country, so check the CDC dog import pages before you travel.^37,16,38,39
• Travel to the EU (as of 2026): the chip must be placed and scanned before the rabies vaccine. Dogs with a non-ISO chip need a scanner that reads it or a second, ISO chip. After a first rabies vaccine, dogs must wait at least 21 days before travel.⁴⁰
• UK (as of 2026): all dogs in the UK must be microchipped and registered on an approved database by 8 weeks of age, and owners can be fined up to £500. England, Scotland and Wales made dog microchipping compulsory in April 2016.^18,41
• US cities and states set their own licensing rules, and many require a license tag on the collar.²⁹

Frequently Asked Questions

How much does it cost to microchip a dog?

Usually about $25 to $50, often including registration.

Does microchipping hurt a dog?

Only briefly, like a vaccine. No sedation is needed.

Can a microchip track my dog's location?

No. You need a GPS tracker for that.

How can I tell if my dog is microchipped?

Check your records, or ask any vet or shelter to scan your dog.

Do dog microchips expire?

No. They have no battery and are designed to last a lifetime. Rarely, a chip stops working, so ask your vet to scan it at checkups, and keep your contact details current.