The Dexcom G6 continuous glucose monitoring (CGM) system is a widely-used tool for people with diabetes to track glucose levels in real time. Its convenience and accuracy have made it a staple in modern diabetes management. However, like any advanced medical device, it can occasionally encounter errors that interrupt readings or degrade performance. Knowing how to identify and resolve these common errors quickly is essential for maintaining accurate data and preventing unnecessary sensor waste. This guide covers the most frequent Dexcom G6 sensor errors, detailed troubleshooting steps, and proactive strategies to keep your system running smoothly.

Understanding the Dexcom G6 System Components

Before diving into troubleshooting, it helps to understand the key components: the sensor (inserted into the skin), the transmitter (snaps onto the sensor and communicates wirelessly), and the display device (usually a smartphone or Dexcom receiver). Errors can originate from any of these parts, and isolating the problem is the first step to fixing it.

Sensor-Side Issues

The sensor is the most delicate component. It contains a tiny filament that sits in interstitial fluid to measure glucose. Errors related to the sensor often indicate a physical or electrical problem. Common sensor-related error messages include “Sensor Error,” “Brief Sensor Issue,” or “Replace Sensor.”

Common Causes:

  • Improper insertion – the applicator may not have been pressed firmly enough, or the sensor may have been inserted at an awkward angle.
  • Sensor dislodgment – if the adhesive fails, the sensor can lift away from the skin, breaking the electrical connection.
  • Expired or damaged sensor – sensors have a limited shelf life and can be physically damaged during shipping or storage.
  • Debris or moisture under the sensor – dirt, sweat, or water can interfere with the sensor’s readings.

Troubleshooting Steps for Sensor Errors:

  1. First, check the application site. If the sensor appears lifted or the adhesive is peeling, apply an overpatch if you have one, but be aware that this may not restore proper function. Often a replacement sensor is needed.
  2. Gently press on the sensor area (without pushing the filament deeper) to ensure the transmitter is fully engaged. A clicking sound often confirms proper connection.
  3. If the “Sensor Error” message persists for more than 30 minutes, remove the sensor and contact Dexcom for a replacement. Do not try to reuse a faulty sensor.
  4. For a “Brief Sensor Issue” that resolves within a few minutes, you may not need to replace the sensor. This can happen during rapid glucose changes or when the sensor is still warming up.
  5. Always check the expiration date on the sensor package before insertion. Expired sensors are more likely to fail.

The Dexcom G6 is factory calibrated and typically does not require fingerstick calibration. However, you may occasionally see a “Calibration Error” message or be prompted to enter a blood glucose value. This usually happens when the system detects an inconsistency between the sensor signal and the expected glucose values.

If a calibration is required (for example, after a transmitter replacement or if the system asks for one), follow these steps:

  • Use a reliable blood glucose meter. Wash your hands and use a fresh test strip to avoid contamination.
  • Calibrate when your glucose is stable – ideally when it’s not rising or falling rapidly (e.g., after fasting, not after meals or exercise).
  • Enter the calibration value exactly as shown on your meter. Rounded or approximated values can introduce errors.
  • If you receive a calibration error repeatedly, do not keep calibrating. Remove the sensor and start a new one. Forcing a calibration can lead to inaccurate readings.

Why Calibration Errors Occur:

  • Rapid glucose changes: the sensor’s interstitial fluid lags behind blood glucose by several minutes. Calibrating during a rapid rise or fall can cause a mismatch.
  • Meter inaccuracy: not all meters are equally accurate. Use a meter that has good accuracy standards (e.g., ISO 15197:2013 compliant).
  • Sensor signal degradation: toward the end of the 10-day wear period, sensor sensitivity may decrease, leading to calibration prompts.

Transmitter and Connectivity Errors

The transmitter is the brain of the CGM system. It collects raw data from the sensor and wirelessly sends it to your display device via Bluetooth Low Energy (BLE). Connectivity issues are among the most frustrating because they can cause data gaps without an explicit error message.

Bluetooth Connection Problems

Symptoms: The app shows “No Readings” for an extended period, or you see a “Signal Loss” message. The transmitter may not be paired, or the connection may be intermittent.

Detailed Troubleshooting:

  1. Ensure Bluetooth is enabled on your smartphone or receiver. On some Android devices, Bluetooth can be turned off by battery-saving modes.
  2. Check that the Dexcom app is not blocked by system-level battery optimization. Add the app to your device’s “unrestricted” or “no optimization” list in battery settings.
  3. Close the Dexcom app completely and reopen it. Sometimes the app’s background process stops communicating.
  4. Restart your phone or receiver. This refreshes the Bluetooth stack and can resolve transient issues.
  5. Move the display device closer to the transmitter (within 20 feet or 6 meters, with no major obstructions). The transmitter’s signal is relatively low power; walls and metal objects can interfere.
  6. If connection still fails, remove the transmitter from the sensor (if you have a spare transmitter, you can test with that) and re-pair it. In the Dexcom app, go to Settings > Transmitter > Pair New Transmitter.
  7. Update your Dexcom app and phone firmware. Older versions may have bugs that affect connectivity.

Transmitter Battery Drain Issues

The Dexcom G6 transmitter has a non-replaceable battery that lasts about three months. When the battery is low, you may see a “Transmitter Low Battery” warning. The transmitter will still work for a while, but eventually it will shut down. If you get a low battery message, plan to replace the transmitter soon. Do not try to recharge it – it’s sealed and not user-serviceable.

The software running on your smartphone or receiver can also produce errors. Common app problems include “App Not Responding,” “Unexpected Error,” or alarms that won’t stop.

Fixing App Issues:

  • Force close the Dexcom app and restart it. On iOS, swipe up from the bottom of the screen and flick the app away. On Android, go to Settings > Apps > Dexcom G6 > Force Stop.
  • Clear the app cache (Android only): Settings > Apps > Dexcom G6 > Storage > Clear Cache. This does not delete your data.
  • Reinstall the app. Download the latest version from the official app store. After reinstalling, you will need to pair your transmitter again.
  • Check for phone compatibility. The Dexcom G6 app supports specific phone models and operating system versions. Using an unsupported device can lead to frequent crashes.
  • If alarm errors occur (e.g., false high/low alarms), verify your alert thresholds in the app settings. Sometimes the thresholds reset after an update.

External factors can mimic or cause sensor errors. The sensor is designed to stay on the skin for up to 10 days, but skin irritation, moisture, and temperature extremes can affect performance.

Adhesion and Skin Issues

Poor adhesion leads to sensor movement, which can cause “Sensor Error” or inaccurate readings. To improve adhesion:

  • Clean the application site with soap and water (not moisturizing soap) and let it dry completely before insertion. Avoid alcohol wipes if they cause irritation.
  • Consider using a medical-grade adhesive overpatch (Dexcom or third-party). Apply the overpatch immediately after inserting the sensor, before any lifting occurs.
  • For sensitive skin, try a barrier film or a skin-prep wipe to reduce irritation. Dexcom offers specific skin prep products.
  • If you experience allergic reactions to the adhesive, consult your healthcare provider. You may need to use a different CGM system.

Temperature and Humidity

Extreme temperatures can cause sensor inaccuracies. The Dexcom G6 is tested for use between 50°F and 104°F (10°C to 40°C). If you are in very cold or hot conditions, the sensor may produce erratic readings or error messages. Try to keep the sensor area covered and protected from direct sunlight or freezing temperatures. Similarly, high humidity can loosen the adhesive – use an overpatch.

Managing Sensor Errors: A Systematic Approach

When you encounter any error, follow this systematic workflow to minimize downtime:

  1. Identify the error message. Take note of the exact wording. Different errors require different fixes.
  2. Wait 10-15 minutes. Many sensor errors, especially “Brief Sensor Issue,” resolve on their own as the sensor adjusts to the body.
  3. Check physical connections. Ensure the transmitter is fully snapped onto the sensor. The sensor should be flush against the skin.
  4. Check Bluetooth and device settings. Make sure Bluetooth is on, the app is running, and the device is within range.
  5. Restart the system. Turn off Bluetooth on your phone, wait 30 seconds, turn it back on. If that fails, restart the phone.
  6. Calibrate only if prompted. Do not calibrate just because you see an error – that can worsen the situation.
  7. Replace the sensor if the error persists. Do not use a sensor that shows continuous errors for more than 30 minutes. Contact Dexcom for a replacement using the serial number.

Preventive Maintenance Tips

To reduce the frequency of errors, incorporate these habits into your routine:

  • Always store sensors in a cool, dry place. Avoid leaving them in a hot car or direct sunlight.
  • Rotate insertion sites. Using the same spot repeatedly can lead to scar tissue and poor sensor performance. Recommended sites: abdomen or upper buttocks (in children). Avoid areas near the waistline or where clothing may rub.
  • Before inserting a new sensor, inspect the package for damage. If the sterile seal is broken, do not use it.
  • Keep the transmitter charged (the battery lasts ~3 months; note the start date). When you replace a transmitter, write down the replacement date so you can anticipate low battery warnings.
  • Update the Dexcom app as soon as new versions are released. Updates often include bug fixes and connectivity improvements.
  • Use a backup method for glucose monitoring, such as a fingerstick meter, especially when you are prone to sensor errors.

When to Contact Dexcom Customer Support

Despite your best efforts, some errors require professional assistance. Contact Dexcom support if:

  • You have replaced a sensor but the same error persists (could indicate a transmitter issue).
  • The transmitter will not pair after multiple attempts.
  • The app crashes repeatedly on a supported device.
  • You suspect a manufacturing defect. Dexcom will often replace faulty sensors or transmitters free of charge.

Dexcom’s support team can be reached via phone or online chat. Their website has a dedicated support portal with troubleshooting guides and community forums. You can also find detailed instructions in the Dexcom G6 user manual.

Understanding Error Codes: Specific Types

The Dexcom G6 may display specific error codes or phrases. Here are the most common ones and what they mean:

  • “Sensor Error – Replace Sensor”: The sensor has failed and cannot recover. This can happen if the filament is broken, the transmitter connection is lost, or the sensor is defective. Replace the sensor immediately.
  • “Brief Sensor Issue”: A temporary glitch, often lasting 10-20 minutes. No action is usually required. It can occur during rapid glucose changes or when the sensor is under physical stress (pressure, bumping).
  • “Calibration Error”: The entered blood glucose value does not match the sensor’s expected range. Re-check your calibration technique or wait for stable glucose levels.
  • “Signal Loss”: No data for up to 30 minutes. Usually a Bluetooth issue or the device is out of range. Restarting Bluetooth or moving closer often fixes it.
  • “Transmitter Low Battery”: The transmitter battery is critically low. Replace the transmitter soon (within a few days).
  • “App Error”: The app has crashed or encountered a critical bug. Reinstalling the app typically resolves this.

Conclusion

The Dexcom G6 is a reliable and life-changing tool, but no medical device is perfect. Sensor errors, calibration prompts, and connectivity problems can occur, but they are usually manageable with systematic troubleshooting. By understanding the root causes—physical connection, Bluetooth interference, software glitches, or environmental factors—you can resolve most issues quickly and get back to accurate glucose monitoring. Remember to follow the user manual, keep your app updated, and don’t hesitate to contact Dexcom support for persistent problems. With the right approach, you can minimize disruptions and maximize the benefit of your CGM technology.