CGM Reading Errors: What They Mean
This article provides general information about CGM reading errors meaning and troubleshooting. Always consult your healthcare provider or CGM manufacturer’s support line for specific medical advice.
Seeing an error message on your Continuous Glucose Monitor (CGM) can be frustrating and concerning. Understanding these CGM reading errors and their meaning is essential for maintaining accurate blood sugar readings and peace of mind. Let’s walk through the most common CGM reading errors and what to do when you see them.
Common CGM Reading Errors and Their Meaning
Your CGM might show different types of errors depending on your device brand. Here are the most frequent ones you might encounter:
- ??? or — Signal – Your CGM can’t communicate with your receiver
- Sensor Error – Something’s wrong with your sensor readings
- Replace Sensor – Your sensor needs to be changed
- Calibration Required – Your device needs a fingerstick reading
Understanding Error Types
Communication Errors:
- Signal loss
- Out of range
- Bluetooth disconnected
- Interference detected
Sensor Errors:
- Temperature extremes
- Sensor failure
- End of life
- Physical damage
Calibration Errors:
- Time for check
- Reading mismatch
- Startup required
- Accuracy verification
What to Do When You See Error Messages
Let’s break down each error with simple steps to resolve them:
Signal Loss Errors
Keep your receiver within 20 feet of your sensor for best results!
When you see this error:
- Check if your receiver is close enough to your sensor
- Make sure nothing’s blocking the signal (like metal or water)
- Wait 10 minutes – sometimes the signal returns on its own
- If the error persists, try moving to a different location
Common Causes:
- Too far from sensor
- Phone in airplane mode
- Bluetooth turned off
- Metal interference
- Water submersion
Quick Fixes:
- Move closer to sensor
- Check Bluetooth settings
- Remove metal objects
- Restart your device
- Wait and retry
Sensor Error Messages
“Sensor Error” or “Check Sensor”
This usually means:
- Sensor isn’t reading properly
- Insertion site problem
- Sensor damage
- Electronic malfunction
What to Do:
- Check sensor placement – Is it secure?
- Look for visible damage
- Clean around sensor gently
- Wait 15-30 minutes
- Replace if error continues
💡 Pro Tip: Keep a backup glucose meter handy for times when your CGM shows errors.
Replace Sensor Notifications
When You See “Replace Sensor”:
Immediate Actions:
- Note the date – Is it day 10 or 14?
- Check your supplies
- Plan replacement time
- Use meter temporarily
Common Reasons:
- Sensor reached end of life
- Early sensor failure
- Adhesive coming loose
- Water damage
- Impact damage
Before Replacing:
- Document for warranty
- Take photos if damaged
- Contact support if early failure
- Check Medicare coverage
Calibration Required
Understanding Calibration Errors:
Some CGMs need periodic calibration with fingerstick readings.
When You See This:
- Wash your hands thoroughly
- Use your glucose meter
- Enter the exact number
- Wait 15 minutes
- Check if error clears
Calibration Best Practices:
- Calibrate when stable
- Avoid after meals
- Use same hand for consistency
- Enter immediately
- Document readings
Device-Specific Error Messages
Dexcom G6/G7 Errors
“Signal Loss”
- Move device closer
- Check Bluetooth
- Restart app
- Replace transmitter battery
“Sensor Failed”
- Remove sensor
- Contact Dexcom
- Use backup supplies
- Document for replacement
“Brief Sensor Issue”
- Wait 3 hours maximum
- Don’t remove sensor
- Check periodically
- Use meter if needed
“No Readings Alert”
- Temporary issue
- Usually self-resolves
- Wait 10 minutes
- Check connection
FreeStyle Libre Errors
“Sensor Error”
- Try scanning again
- Check sensor security
- Clean reader lens
- Replace if persistent
“Check Sensor”
- Sensor ending soon
- Prepare replacement
- Continue scanning
- Note expiration time
“New Sensor Not Ready”
- 60-minute warm-up required
- Wait full time
- Don’t scan early
- Set timer reminder
“Replace Sensor”
- 14 days complete
- Must replace now
- Cannot extend
- Apply new sensor
Medtronic Guardian Errors
“Sensor Updating”
- Normal occurrence
- Wait 10-20 minutes
- Continue normal activities
- Will auto-resolve
“Cal Error”
- Calibration rejected
- Wait 15 minutes
- Recalibrate carefully
- Check meter accuracy
“Change Sensor”
- End of sensor life
- Replace immediately
- Cannot override
- Have backup ready
Troubleshooting by Error Pattern
Frequent Signal Loss
If This Happens Often:
Check Your Environment:
- Microwave interference
- Metal furniture nearby
- Water exposure
- Electronic devices
Solutions:
- Change locations
- Adjust device position
- Update software
- Consider interference
Repeated Sensor Errors
Possible Causes:
- Site rotation needed
- Skin sensitivity
- Application technique
- Storage issues
Prevention Tips:
- Rotate sites properly
- Clean skin thoroughly
- Let alcohol dry completely
- Store sensors correctly
- Check expiration dates
Calibration Problems
If Calibrations Keep Failing:
- Verify meter accuracy
- Check test strip dates
- Time calibrations better
- Clean meter and hands
- Use control solution
When to Call for Help
Contact Manufacturer Support:
Immediate Issues:
- Multiple sensor failures
- Transmitter not working
- App crashes repeatedly
- Unknown error codes
Documentation Needed:
- Error messages
- Serial numbers
- Purchase dates
- Previous troubleshooting
Medicare Replacement Coverage
What’s Covered:
- Defective sensors
- Early failures
- Manufacturer defects
- Approved replacements
Not Covered:
- User damage
- Lost sensors
- Expired products
- Improper storage
For Medicare CGM coverage questions, call Senior CGM Support at 727-831-3729.
Prevention Strategies
Daily Maintenance
Morning Routine:
- Check sensor adhesion
- Verify device charged
- Test connection
- Note any issues
Evening Check:
- Review day’s errors
- Charge devices
- Check supplies
- Plan ahead
Weekly Tasks
Prevent Problems:
- Update apps
- Check expiration dates
- Inventory supplies
- Clean devices
- Review patterns
Proper Storage
Sensor Storage:
- Room temperature
- Original packaging
- Away from moisture
- Check dates monthly
- First in, first out
Emergency Backup Plans
When CGM Fails Completely
Immediate Actions:
- Use backup meter
- Check supplies
- Contact support
- Document issue
- Monitor manually
Temporary Management:
- Increase fingersticks
- Set phone alarms
- Track in log
- Stay vigilant
- Order replacements
Creating Your Error Response Plan
Write Down:
- Support numbers
- Error meanings
- Quick fixes
- Backup plans
- Emergency contacts
Keep Handy:
- Printed guide
- Phone numbers
- Backup supplies
- Meter and strips
- Medical information
Understanding Warning vs. Error
Warnings (Yellow/Caution):
- Low battery
- Signal weak
- Calibration due soon
- Sensor expiring
- Update available
Errors (Red/Stop):
- Sensor failure
- No readings
- Replace now
- System error
- Critical malfunction
Tips from Other Seniors
Success Strategies:
Margaret, 71: “I keep a cheat sheet of error messages on my fridge. When I see one, I know exactly what to do.”
Robert, 68: “Setting phone reminders for sensor changes prevents those ‘replace sensor’ surprises.”
Dorothy, 74: “I always calibrate at the same times each day when my blood sugar is stable. Fewer errors!”
Technology Tips
App Management:
- Keep apps updated
- Allow all permissions
- Don’t force close
- Regular restarts
- Clear cache monthly
Phone Settings:
- Bluetooth always on
- Battery optimization off
- Notifications enabled
- Do not disturb exceptions
- Regular backups
Creating Your Troubleshooting Kit
Essential Items:
- Error code list
- Manufacturer contacts
- Backup meter
- Extra test strips
- Alcohol wipes
- Overlay patches
- Documentation forms
Digital Tools:
- Screenshot errors
- Photo documentation
- Error log app
- Support chat access
- Video guides saved
Working with Your Healthcare Team
Share Error Patterns:
- Frequency of errors
- Types most common
- Impact on control
- Troubleshooting tried
- Replacement needs
Questions to Ask:
- Alternative placement options
- Prescription updates needed
- Different device options
- Training resources
- Support services
Long-Term Success
Reducing Errors:
Month 1:
- Learn common errors
- Practice troubleshooting
- Build confidence
- Document issues
Month 2:
- Identify patterns
- Prevent problems
- Optimize settings
- Share successes
Month 3:
- Master troubleshooting
- Help others
- Minimal errors
- Confident management
Quick Reference Guide
Most Common Fixes:
- Signal Loss: Move closer
- Sensor Error: Wait 15 minutes
- Replace Sensor: Check day count
- Calibration: Use fresh strip
- No Readings: Check Bluetooth
Emergency Contacts:
- Dexcom: 1-888-738-3646
- Abbott: 1-855-632-8658
- Medtronic: 1-800-646-4633
- Senior CGM Support: 727-831-3729
The Bottom Line
CGM reading errors meaning are common and usually easy to fix. Don’t let error messages discourage you from using this valuable technology. With this guide and a little practice, you’ll handle errors like a pro.
Remember: When in doubt, you always have backup options and support available.
References
Need Help with Medicare CGM Coverage?
Our specialists can help you navigate Medicare requirements and get the supplies you need.
Call Now: 727-831-3729
Keep this guide handy for quick reference when errors occur. You’ve got this!
