What is the best continuous glucose monitor (CGM) to use for managing diabetes?

Best Continuous Glucose Monitor for Diabetes Management

The Dexcom G6/G7 real-time continuous glucose monitoring (rtCGM) system is the best choice for most people with diabetes requiring glucose monitoring, particularly for those on insulin therapy, due to its FDA approval for treatment decisions without confirmatory blood glucose checks and its integration capabilities with automated insulin delivery systems. 1

Types of Continuous Glucose Monitors

There are several types of CGM systems available:

• Real-time CGM (rtCGM): Continuously measures and displays glucose levels with alarms for hypo/hyperglycemia (e.g., Dexcom G6/G7) 1
• Intermittently scanned CGM (isCGM): Measures glucose continuously but requires scanning for visualization (e.g., FreeStyle Libre) 1
• Professional CGM: Placed by healthcare providers for discrete periods (7-14 days) to assess patterns 1
• Over-the-counter CGM: Biosensors for people with prediabetes or non-insulin-treated diabetes 1

Selection Criteria for CGM Systems

FDA Approval Status

• Only Dexcom G5/G6 systems are FDA-approved for making treatment decisions without confirmatory blood glucose monitoring (BGM) checks 1
• Dexcom G6, Dexcom G7, FreeStyle Libre 2 Plus, and Eversense E3 are FDA approved for use with automated insulin delivery (AID) systems 1

Accuracy Considerations

• CGM accuracy is measured by mean absolute relative difference (MARD) - lower is better 2, 3
• Recent head-to-head comparison showed FreeStyle Libre 3 had better point accuracy than Dexcom G7 (MARD 8.9% vs 13.6%) 3
• Dexcom G7 demonstrated overall MARD of 8.2% for arm placement and 9.1% for abdomen placement in clinical trials 2
• Accuracy may vary in special populations - in hemodialysis patients, FreeStyle Libre 1 showed better accuracy (MARD 11.3%) than Dexcom G6 (MARD 22.7%) 4

Clinical Benefits

• rtCGM in conjunction with intensive insulin regimens lowers HbA1c levels in adults with type 1 diabetes (Grade A recommendation) 1
• rtCGM is particularly beneficial for those with hypoglycemia unawareness or frequent hypoglycemic episodes (Grade B recommendation) 1
• Daily use of rtCGM provides maximal benefit (Grade A recommendation) 1
• Sensor-augmented pump therapy with automatic low-glucose suspend can prevent hypoglycemic episodes in high-risk patients (Grade B recommendation) 1

Specific CGM System Comparisons

Dexcom G6/G7

• Advantages:
  • Provides real-time glucose readings with customizable alerts 5
  • FDA-approved for treatment decisions without confirmatory BGM 1
  • Compatible with automated insulin delivery systems 1
  • Optional features like data sharing improve glycemic outcomes 5
• Limitations:
  • Higher cost compared to isCGM systems 1
  • May read higher than actual blood glucose values 6

FreeStyle Libre Systems

• Advantages:
  • Lower cost than rtCGM systems with alerts 1
  • Newer versions (Libre 2+) include alarms 1
  • May have better point accuracy in some studies 3
• Limitations:
  • Original versions required scanning for glucose readings 1
  • May read lower than actual blood glucose values 6
  • Approved for adult use only (for some versions) 1

Senseonics Eversense

• Advantages:
  • Implanted device providing real-time CGM for 5-6 months 1
  • FDA approved for use with AID systems 1
• Limitations:
  • Requires minor surgical procedure for implantation 1

Special Considerations

Interfering Substances

• Certain medications and conditions can affect CGM accuracy:
  • High doses of acetaminophen (>4g/day), salicylic acid, ascorbic acid may interfere with readings 1
  • Acute physiological disturbances (hypoxemia, vasoconstriction, severe dehydration) 1
• People wearing CGM devices should be educated on potential interfering substances 1

Skin Reactions

• Skin reactions due to irritation or allergy should be assessed and addressed 1

Usage Patterns

• rtCGM should be used daily for maximum benefit 1
• isCGM devices should be scanned at minimum once every 8 hours to avoid data gaps 1

Patient-Specific Recommendations

• Type 1 diabetes on insulin: Dexcom G6/G7 for real-time alerts and integration with insulin pumps 1
• Type 2 diabetes on multiple daily insulin injections: Either rtCGM or isCGM based on need for alerts 1
• Type 2 diabetes on non-insulin therapy: Consider isCGM for cost-effectiveness 1
• Patients with hypoglycemia unawareness: rtCGM with alerts strongly recommended 1
• Patients on hemodialysis: FreeStyle Libre may be more accurate 4