Microchip Migration: When a Chip Moves, and What to Do if It Can't Be Found

If a vet has run a scanner over your pet and found nothing where the chip should be, the chip may simply have moved. If it really can’t be found, there are steps you and your vet can take to locate it.

How far a microchip can move

In the UK, chips for dogs and cats go under the skin on the midline between the shoulder blades, and they sometimes wander from that spot. Our guide to microchip placement in dogs and cats goes into this in more detail.

The only published UK figures come from a Veterinary Medicines Directorate (VMD) review covering 2014 and 2015. Of 1,420 reports in that period, 729 were logged as migrations, and 302 of those were judged likely to be true migrations. The figures are a decade old now, so treat them as a sense of scale rather than a current rate.

The same review gives the clearest picture for cats. Of the 729 migration reports, 53 were in cats and 22 of those were assessed as likely true migrations. In cats, migrations were most often picked up within a year of implantation, but some only came to light between five and ten years later. So if your cat’s chip seems to have moved years after it went in, that fits the pattern.

Why a scan might not find a chip

A blank scan doesn’t always mean a missing chip. The British Small Animal Veterinary Association (BSAVA) says the commonest reason is that the chip came out of the animal shortly after it was implanted, so it was never there to find.

The scanner itself matters as well. Not every scanner reads every chip type: some read ISO FDX-B chips only, while others read more than one chip frequency. This comes up most often with pets chipped abroad.

Where the chip was put in also varies by country. The World Small Animal Veterinary Association (WSAVA) notes that outside continental Europe chips go between the shoulder blades, while in continental Europe the convention is the middle of the left side of the neck. It recommends scanning the alternative site if the first scan finds nothing. If your pet came from overseas, that second site is worth checking.

What to do if your pet's chip can't be found

By the VMD’s definition, a chip has failed only when it is not detected after a full-body scan with a working scanner.

1. Ask for a thorough scan of the whole body, not just the usual spot.
2. Ask the vet to follow WSAVA’s scanning advice: scan for at least 10 seconds, keep at least a metre from other electronics, avoid stainless steel tables, remove metal collars and check the scanner battery.
3. If the pet may have been chipped abroad, ask for the left side of the neck to be scanned as well.
4. Ask for a second scan with a different scanner, ideally one that reads more than one chip type, in case the first scanner can’t read that make of chip.
5. If no scanner finds a chip after a full-body scan, ask the vet about implanting a new one.

By the VMD's definition, a chip has failed only when it is not detected after a full body scan with a working scanner.

1. Ask for a thorough scan of the whole body, not just the usual spot.
2. Ask the vet to follow WSAVA's scanning advice. That means scanning for at least 10 seconds, keeping at least a metre from other electronics, avoiding stainless steel tables, removing metal collars and checking the scanner battery.
3. If the pet may have been chipped abroad, ask for the left side of the neck to be scanned as well.
4. Ask for a second scan with a different scanner, ideally one that reads more than one chip type, in case the first scanner can't read that make of chip.
5. If no scanner finds a chip after a full-body scan, ask the vet about implanting a new one.

If your pet does end up with a new chip, the old one can stay where it is. There’s no need to remove a faulty chip, and the vet can simply place the new one alongside it.

Reporting a chip that has moved or failed

Reports now go to Defra. In England and Wales, vets and trained implanters must report reactions, migrations and failures using the GOV.UK microchipping adverse event reporting form. Owners can report too: the form’s occupation options include “animal owner”, and Defra confirms it receives reports from members of the public as well as vets.

Don’t send the report to the VMD. GOV.UK’s page on reporting animal medicine problems lists microchip problemsunder “what you can’t report” and directs people to Defra instead.

Keeping the record current when a chip is replaced

The chip itself is a permanent implant that holds only a number, with no contact details and no tracking. Your name, phone number and address sit on a database linked to that number: that’s the record, and keeping it current is your part.

If your pet’s chip has stopped reading and needs replacing, the admin is on you. The VMD has said it doesn’t notify microchip databases of failure reports, so you need to update the record when a chip fails or migrates out and has to be replaced. Our page on what to do after your pet is chipped covers the registration side. If you’re not sure which database holds the record, our guide to microchip databases explains how to find out.

On Pet Database, a re-chipped pet can’t simply have its number edited in your account. Add your pet as a new record with the new microchip number, then contact support so the outdated chip details can be removed. If the number on the record was typed incorrectly, that can’t be changed directly in your account either; contact support with your pet’s name, the incorrect number, the correct number and proof of it, such as vet or implanter documentation.

If you still have the chip number from paperwork, you can check what the database record holds. Our guide to finding your pet’s microchip number shows where to look if you don’t have it to hand.

If the chip has moved but still reads, it’s only useful if the record behind it is current. A quick run of the 15-digit number through our chip checker shows which UK database holds it, so you know where to update your details.