Dexcom G7 · FreeStyle Libre 2 & 3
CGM Sensor Errors, Inaccurate Readings & Early Failure
Quick Answer
If your sensor shows an error or readings don’t match your symptoms, check with a fingerstick before treating. The first day of a new sensor can be less accurate. A sensor that ends early should be reported to the manufacturer.
When readings don’t match how you feel
- Always use a blood glucose meter to confirm if your symptoms don’t match your sensor reading, before treating.
- Readings in the first 24 hours of a new sensor may be less accurate.
- Pressure on the sensor while sleeping can cause falsely low readings (“compression lows”).
- Dehydration and some medications can affect readings — check your device’s user guide for interfering substances.
Error messages
- Follow the instructions in your app — many errors (like a temporary sensor error) resolve on their own.
- Note the error text and the time it happened; the manufacturer will ask for it.
- Don’t try to reinsert or reattach a sensor that has come out.
Sensor stopped early
- Remove it and apply a new sensor so you don’t go without readings.
- Keep the old sensor and applicator — the manufacturer may ask for the lot number or for you to return it.
- Report it to the manufacturer for a replacement (see “Getting a Replacement Sensor”).
When to call us
- You have urgent symptoms of low or high blood sugar — contact your doctor or call 911.
- Several sensors fail early in a row — let us and your prescriber know.
General guidance only, not medical advice. Always follow your device’s user guide and your prescriber’s instructions. For urgent symptoms of low or high blood sugar or trouble breathing, call 911.