How accurate are continuous glucose monitors for pets?
Flash glucose monitors are increasingly used on diabetic dogs and cats. What the research says about their accuracy, when to trust them, and when to double-check with a glucometer.
How accurate are continuous glucose monitors for pets?
Species: Both dogs and cats
Continuous glucose monitors (CGMs), including flash glucose monitors, are increasingly used with diabetic dogs and cats. They can give owners and vets a much fuller picture than occasional spot checks — often with far less stress for a cat who hates repeated pricks.
What a CGM actually measures
A sensor measures glucose in the fluid between cells (interstitial glucose), rather than directly in blood. That distinction matters: interstitial glucose follows blood glucose, but it is not the same sample and can lag behind changes.
Research has found good clinical accuracy in pets. In plain English, the readings can be useful for making a care decision and spotting a pattern. That does not mean the number is analytically identical to the number a blood test would give.
Studies have found interstitial glucose can underestimate blood glucose during normal and mildly low readings. Earlier work also found that sensors could overestimate glucose during true low blood sugar. The direction of the difference is not predictable enough to ignore how your pet looks.
What the research found
The evidence is encouraging, but it is not a promise of a perfect sensor. Reported studies found dysfunctional sensors in around 12% of dogs, skin irritation in around 18%, and premature detachment in around 15% of cats. Those figures describe study populations and devices, not a guarantee for your pet.
A CGM is also a human medical device used off-label in animals. It is not approved for veterinary use, and the manufacturer does not provide support or warranty replacement for pet usage. Your vet fits the device, helps you protect it, and interprets the readings in context.
The rule that keeps your pet safe
The rule that keeps your pet safe
If the sensor reads low but your pet seems completely normal, check with a glucometer before acting. If your pet shows signs of low blood sugar — wobbliness, weakness, trembling, confusion — but the sensor reads normal, treat it as real and contact your vet. Trust your pet over the sensor.
How to use the information well
Log sensor readings alongside meals, insulin, activity, symptoms and anything unusual. A single number is less useful than a pattern with context. Mello helps you keep that record together so your vet can see what was happening around a rise or fall.
A sensor is one part of the care plan, not a replacement for your vet or for blood verification when the reading does not fit the clinical picture.
Sources
- Tardo AM, Crews C, Mott J, et al. “Accuracy of the FreeStyle Libre 3 Continuous Glucose Monitoring System in Hypo- and Euglycemic Cats.” Journal of Veterinary Internal Medicine, 2025;39:e70048.
- Berg AS, Crews CD, Adin C, et al. “Assessment of the FreeStyle Libre 2 interstitial glucose monitor in hypo- and euglycemic cats.” Journal of Veterinary Internal Medicine, 2023;37(5):1703–1709.
This guide is for educational purposes and is not a substitute for professional veterinary advice. Always consult your veterinarian before changing insulin, responding to a glucose reading, or fitting a sensor.
Keep the full picture in one place. Join the early-access list to track glucose readings, meals, insulin and symptoms together.
Frequently asked questions
Are CGMs accurate enough for pets?
They can be clinically useful, but they do not produce the same number as a blood test every time. Your vet should help you understand the device's limitations and when to verify a reading.
Can I use a human FreeStyle Libre on my dog or cat?
A vet may recommend one off-label, but it is not approved for animal use. Do not fit or interpret one without veterinary guidance.
How long do sensors last on pets?
It depends on the device, the fit and your pet. Sensors can detach early, so ask your vet what to expect and how to protect the site.
What do I do if the sensor reading does not match how my pet seems?
Check a surprising low reading with a glucometer if your pet seems normal. If your pet shows signs of hypoglycaemia, treat that as real and contact your vet even if the sensor says otherwise.
Are CGMs better than a glucometer?
Neither is simply better. CGMs show trends with less handling; glucometers provide a blood reading that can verify an unexpected result.
Reviewed by your veterinary team before acting.
Read our guide to home glucose monitoring or learn about SGLT2 inhibitors for diabetic cats.
Get daily diabetes care insights. Join the early-access list to keep the routine clear.
When to contact your vet
- Contact your vet promptly if your pet’s symptoms, appetite, drinking, urination, behaviour or glucose readings change unexpectedly.
- Ask your vet for advice before changing insulin, food, exercise or any other part of your pet’s routine.
- Seek urgent veterinary care for collapse, seizures, severe weakness, repeated vomiting, or suspected hypoglycaemia or diabetic ketoacidosis.
Quick answers
What's Next?
Continue your diabetes management journey with these recommended next steps.
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Keep your care organised
Mello is being built for calm, consistent tracking before the app launches.
Mello is a tracking and communication tool, not a substitute for veterinary advice. Always consult your vet for medical decisions about your pet.
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