CGM Sensor Failed? Here Is What to Do

When Your CGM Sensor Fails: Stay Calm and Take Action

Continuous glucose monitors have transformed diabetes management, but sensor failures do happen. Whether you see an error message, get no readings, or notice wildly inaccurate data, knowing exactly what to do next can prevent a dangerous gap in your monitoring. This guide walks you through every step — from immediate troubleshooting to long-term prevention.

Common Signs of a CGM Sensor Failure

Not every problem is a true failure. Recognizing the difference between a glitch and a genuine sensor malfunction helps you respond appropriately.

• No readings for 30+ minutes after successful warm-up
• "Sensor Error" or "Failed Sensor" alerts on your receiver or app
• Glucose readings that don't match how you feel — or fingerstick results are wildly different
• Constant "Signal Loss" even when the transmitter is nearby
• Sensor fell off or adhesive detached prematurely

Step 1: Verify It Is Actually the Sensor

Before replacing your sensor, rule out other causes. Check that your transmitter is fully charged and snapped in securely. Restart your receiver or phone app and move it within range. Confirm the sensor session is still active and hasn't simply expired. Sometimes a quick restart resolves communication errors without wasting a sensor.

Step 2: Perform a Fingerstick Check

During any sensor error, revert to fingerstick blood glucose testing immediately. This is critical — never dose insulin or make major treatment decisions based solely on a sensor you suspect is failing. Keep a reliable glucometer and test strips accessible at all times as a backup.

Step 3: End the Session and Replace the Sensor

If the error persists after troubleshooting, end the sensor session in your app or receiver and insert a new sensor. Follow the manufacturer's insertion instructions carefully — placement matters. Most sensors require a warm-up period of 30 minutes to 2 hours before delivering readings.

Tips for a Successful New Insertion

• Choose a fresh site at least 3 inches from your last sensor location
• Clean the skin with an alcohol wipe and allow it to dry completely before inserting
• Avoid areas with scar tissue, waistbands, or high movement
• Press the adhesive firmly around the edges to ensure a secure hold

Step 4: Contact the Manufacturer for a Replacement

Most CGM manufacturers — including Dexcom, Libre, and Medtronic — have warranty programs that replace failed sensors at no charge. Document the error message, time, and lot number on the sensor packaging before discarding it. Call their support line or submit a request online. Keep track of replacements, as repeated failures from the same batch may indicate a manufacturing issue worth reporting.

Preventing Future Sensor Failures

Many failures are preventable with good habits:

• Store sensors at the recommended temperature — avoid cars, direct sunlight, or freezing conditions
• Check expiration dates before opening a new sensor
• Rotate insertion sites consistently to allow tissue recovery
• Use medical-grade skin-prep wipes or overtape products to extend adhesion in hot or humid conditions
• Source sensors from trusted suppliers to avoid counterfeit or improperly stored products

Where to Get Reliable CGM Sensors

Sensor quality and proper storage throughout the supply chain directly affect performance. At mdsdiabetes.com, CGM sensors are handled and stored according to manufacturer specifications, giving you confidence that every sensor you receive is ready to perform. Whether you use Dexcom G6, G7, or FreeStyle Libre, stocking up from a reliable source reduces the risk of storage-related failures before the sensor even reaches your skin.

When to Call Your Healthcare Provider

If you experience frequent sensor failures, unusual skin reactions at insertion sites, or difficulty managing glucose during downtime, contact your diabetes care team. They can help you evaluate whether your current CGM system is the best fit and guide you through any clinical concerns.