CGM sensors occasionally fail before their approved wear period ends. Both Dexcom and Abbott have replacement programs — here is how to document a failure and request a replacement effectively.
Types of Sensor Failures
- No insertion signal: Sensor does not connect after correct application
- Early termination: Sensor stops transmitting before day 10 (G7) or day 14 (Libre 3)
- Persistent signal loss: Intermittent, irrecoverable connection drops that require sensor removal
- Accuracy failure: Consistent readings more than 20% different from fingerstick that do not correct
- Application failure: Sensor falls off during insertion or within the first few days despite correct technique
What to Document Before Calling
- Sensor lot number (on the packaging)
- Sensor serial number (displayed in the app under sensor information)
- Date of application and date of failure
- Error message shown in the app (take a screenshot)
- Brief description of what happened
Dexcom Replacement Process
Contact Dexcom customer support: 1-888-738-3646 (US) or via the support chat in the G7 app. Provide the lot number and sensor serial. For most failures within the approved wear period, a replacement is shipped at no charge within 1-3 business days. Dexcom does not require you to return the failed sensor.
Abbott (FreeStyle Libre) Replacement Process
Contact Abbott Diabetes Care: 1-855-632-8658 (US) or via myfreestyle.com. Same process — lot number, description of failure. Abbott typically processes replacements within 2-3 business days.
Failure Rate Reality
Both manufacturers quote failure rates under 2% in clinical data. Real-world community reports suggest slightly higher rates — perhaps 3-5% across all failure modes — for sensors used in active lifestyles. Both companies are generally responsive to legitimate replacement requests.
Preventing Common Failures
- Store sensors at room temperature (not in car gloveboxes in summer heat)
- Check expiration date before applying
- Ensure alcohol wipe site is completely dry before application
- Apply to a site without scar tissue from previous sensors