Fifteen years in DME means I’ve seen pretty much every CGM platform come through — the launches, the glitches, the updates Abbott and Dexcom never quite communicated to patients. I know what actually goes wrong with these devices for seniors and what you can fix yourself. That’s what I’m writing about here.

— Susie Adriance, founder of Senior CGM Support

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

American Diabetes Association

CDC – Diabetes

NIH/NIDDK – Diabetes Information

National Institute on Aging – Diabetes in Older People

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!

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