Why you should report faulty CGM sensors to the MHRA, not just to the manufacturer
Kevin's post has clearly struck a chord, so here's something practical. If your CGM sensor fails early, gives readings that don’t match a fingerprick test (ideally taken when your glucose levels are steady), drops its connection, won't stay stuck on, or the adhesive irritates your skin, in the United Kingdom please report it to the medical devices regulator, the Medicines and Healthcare products Regulatory Agency ("MHRA") through the "Yellow Card" scheme. Do this as well as contacting the manufacturer, not instead of it.
Why the MHRA?
1. It's the regulator. The MHRA is the UK government agency responsible for making sure medical devices work and are acceptably safe. The manufacturer's customer services can deal with your sensor. Only the regulator can push for changes to the product.
2. They've asked us to. In October 2024 the MHRA publicly asked CGM and insulin pump users to report safety problems "without delay". Its guidance for diabetes device users specifically lists adhesive failure, reactions to the adhesive, and devices that don't work for their full expected lifespan as things to report.
3. They hardly hear from us. The MHRA said it had received fewer than 300 Yellow Card reports from patients and health professionals about these diabetes medical devices, far fewer than the MHRA would expect given how many people use them. It gets more reports from the manufacturers themselves. In other words, the regulator mostly sees the manufacturers' side of the story.
4. Reports carry legal weight. In Great Britain, under the Medical Devices Regulations 2002, strengthened from June 2025, the MHRA must record reports of incidents. If it notifies the manufacturer about a reported incident, the manufacturer must consider whether it's a "serious incident". If the manufacturer says it isn't, it has to explain why. If the MHRA disagrees, the manufacturer must treat it as serious. The MHRA must also monitor reports for trends. When it flags a risk, the manufacturer must investigate and report back on what it's doing about it.
5. Numbers make patterns. One failed sensor can be put down to bad luck. Hundreds of reports of the same fault with the same product make a trend, and trends lead to safety notices, investigations and design changes. The MHRA's own guidance describes a case where a rise in reports of skin reactions to CGM sensors led the manufacturer to change its adhesive, and reported skin reactions then fell.
6. It's free and quick. Report online at http://www.mhra.gov.uk/yellowcard or on the free Yellow Card app. Most fields are optional.
What to include if you can:
1. the device and model
2. the sensor serial or lot number
3. the date you applied it and the date it failed or came off
4. what happened
5. fingerprick readings next to the CGM readings, with the times
6. (if possible) photos
7. any case reference the manufacturer gave you
Keep the faulty sensor if you can. Give consent for your report to be shared with the manufacturer. With your consent, the MHRA sends it to the manufacturer to investigate.
Be realistic: the MHRA won't get you a replacement, and it won't tell you how the manufacturer's investigation turned out. So do all of these:
1. Contact Abbott UK Customer Service (FreeStyle Libre) on 0800 170 11 77. Ask for a replacement and a reference number for your complaint.
2. Make a Yellow Card report, so the problem is on the regulator's official record.
3. If the fault affected your health, for example a hypo or a high you didn’t know about, say so in your Yellow Card report and tell your GP or diabetes team.
The manufacturer's customer service deals with your sensor. The regulator deals with the product.
If we want things to change, the MHRA needs to hear from us.
Kevin's post has clearly struck a chord, so here's something practical. If your CGM sensor fails early, gives readings that don’t match a fingerprick test (ideally taken when your glucose levels are steady), drops its connection, won't stay stuck on, or the adhesive irritates your skin, in the United Kingdom please report it to the medical devices regulator, the Medicines and Healthcare products Regulatory Agency ("MHRA") through the "Yellow Card" scheme. Do this as well as contacting the manufacturer, not instead of it.
Why the MHRA?
1. It's the regulator. The MHRA is the UK government agency responsible for making sure medical devices work and are acceptably safe. The manufacturer's customer services can deal with your sensor. Only the regulator can push for changes to the product.
2. They've asked us to. In October 2024 the MHRA publicly asked CGM and insulin pump users to report safety problems "without delay". Its guidance for diabetes device users specifically lists adhesive failure, reactions to the adhesive, and devices that don't work for their full expected lifespan as things to report.
3. They hardly hear from us. The MHRA said it had received fewer than 300 Yellow Card reports from patients and health professionals about these diabetes medical devices, far fewer than the MHRA would expect given how many people use them. It gets more reports from the manufacturers themselves. In other words, the regulator mostly sees the manufacturers' side of the story.
4. Reports carry legal weight. In Great Britain, under the Medical Devices Regulations 2002, strengthened from June 2025, the MHRA must record reports of incidents. If it notifies the manufacturer about a reported incident, the manufacturer must consider whether it's a "serious incident". If the manufacturer says it isn't, it has to explain why. If the MHRA disagrees, the manufacturer must treat it as serious. The MHRA must also monitor reports for trends. When it flags a risk, the manufacturer must investigate and report back on what it's doing about it.
5. Numbers make patterns. One failed sensor can be put down to bad luck. Hundreds of reports of the same fault with the same product make a trend, and trends lead to safety notices, investigations and design changes. The MHRA's own guidance describes a case where a rise in reports of skin reactions to CGM sensors led the manufacturer to change its adhesive, and reported skin reactions then fell.
6. It's free and quick. Report online at http://www.mhra.gov.uk/yellowcard or on the free Yellow Card app. Most fields are optional.
What to include if you can:
1. the device and model
2. the sensor serial or lot number
3. the date you applied it and the date it failed or came off
4. what happened
5. fingerprick readings next to the CGM readings, with the times
6. (if possible) photos
7. any case reference the manufacturer gave you
Keep the faulty sensor if you can. Give consent for your report to be shared with the manufacturer. With your consent, the MHRA sends it to the manufacturer to investigate.
Be realistic: the MHRA won't get you a replacement, and it won't tell you how the manufacturer's investigation turned out. So do all of these:
1. Contact Abbott UK Customer Service (FreeStyle Libre) on 0800 170 11 77. Ask for a replacement and a reference number for your complaint.
2. Make a Yellow Card report, so the problem is on the regulator's official record.
3. If the fault affected your health, for example a hypo or a high you didn’t know about, say so in your Yellow Card report and tell your GP or diabetes team.
The manufacturer's customer service deals with your sensor. The regulator deals with the product.
If we want things to change, the MHRA needs to hear from us.
