Alternatives to Dexcom G7 for Continuous Glucose Monitoring
The primary alternatives to Dexcom G7 are the FreeStyle Libre systems (Libre 2, Libre 2 Plus, and Libre 3), Medtronic Guardian systems (Guardian Connect and Guardian 4), and the Eversense E3 implantable CGM, all of which are FDA-approved for diabetes management with varying features and clinical applications. 1
Real-Time CGM Alternatives
FreeStyle Libre Systems (Abbott)
- FreeStyle Libre 2 Plus and Libre 3 are FDA-approved for integration with automated insulin delivery (AID) systems, similar to Dexcom G7 1
- The Libre 3 provides real-time glucose values every minute, though it is not currently interoperable with AID systems despite its iCGM designation 2
- FreeStyle Libre systems use wired glucose oxidase-based enzyme technology that operates at very low voltage, reducing susceptibility to acetaminophen interference at therapeutic levels 3
- Recent head-to-head comparison showed FreeStyle Libre 3 demonstrated significantly lower MARD (8.9%) compared to Dexcom G7 (13.6%), with 91.4% vs 78.6% of glucose values within ±20 mg/dL of reference 4
- These systems are factory-calibrated and do not require fingerstick calibrations, reducing monitoring burden 5
- Important limitation: FreeStyle Libre should NOT be used in patients receiving peritoneal dialysis due to potential icodextrin interference 3
Medtronic Guardian Systems
- Guardian Connect with Enlite Sensor is available as a user-calibrated real-time CGM system 1, 6
- The Guardian 4 (7-day wear) represents the newer generation expected to launch with automatic initialization and easy insertion 2
- In comparative studies, Guardian Connect showed overall MARD of 9.7% with 98.6% of values in Clarke Error Grid zones A+B 6
- Guardian systems require four capillary blood glucose calibrations per day, unlike factory-calibrated alternatives 6
- These systems demonstrated 78.9% sensitivity and 93.4% specificity for hypoglycemia detection 6
Eversense E3 Implantable CGM
- Eversense E3 is the only implantable CGM system, FDA-approved for 6 months of continuous use 1, 2
- This system is FDA-approved for use with automated insulin delivery systems 1
- Requires a minor surgical procedure for implantation, which may affect insurance coverage patterns differently than transcutaneous sensors 5
- Particularly useful for patients with skin reactions or adhesive allergies to traditional sensors 1
Intermittently Scanned CGM (isCGM) Options
FreeStyle Libre (First Generation)
- Functions as intermittently scanned CGM without real-time alarms, requiring user-initiated scanning 6
- Demonstrated MARD of 17.5% in comparative studies, with 98.1% of values in acceptable error grid zones 6
- Sensors must be scanned at minimum once every 8 hours to avoid gaps in data 1
- More affordable option but less effective for hypoglycemia prevention compared to real-time systems 6
Clinical Performance Comparisons
Real-Time vs Intermittently Scanned Systems
- Real-time CGM (rtCGM) demonstrates superior outcomes compared to intermittently scanned CGM (isCGM) in three randomized controlled trials 1
- rtCGM showed greater reduction in time spent in hypoglycemia (<70 mg/dL and <54 mg/dL) compared to isCGM 1
- rtCGM achieved higher time-in-range (70-180 mg/dL) and lower A1C levels at 12 months compared to isCGM 1
- In head-to-head comparison, time below range was 10.5% for FreeStyle Libre (FGM) versus 2% for Guardian Connect (rtCGM), highlighting the hypoglycemia detection advantage of real-time systems 6
Accuracy Considerations by Clinical Context
- Arm placement may provide better accuracy than abdomen or other sites for most CGM systems 2
- Lag time between sensor and actual glucose ranges from 2-3 minutes in optimal conditions but can extend to 15-20 minutes when glucose rate of change exceeds 2 mg/min 2
- For patients with advanced chronic kidney disease on hemodialysis, all CGM systems should be used with caution, focusing on pattern assessment rather than specific glucose values 1
Insurance Coverage and Access
Medicare and Commercial Insurance
- Both Dexcom G6/G7 and FreeStyle Libre systems have achieved broad insurance coverage, including Medicare eligibility 5
- Medicare requires documentation that CGM continuously measured glucose >95% of the time for ongoing coverage 5
- Factory-calibrated systems reduce overall monitoring costs by eliminating fingerstick calibration requirements 5
Cost Considerations
- Real-time CGM systems generally have higher direct costs than intermittently scanned systems 5
- In user surveys, only 30% of patients expressed willingness to use either device continuously due to sensor costs 6
- Eversense implantable CGM may have different coverage patterns due to the surgical implantation requirement 5
Special Population Considerations
Pregnancy
- Dexcom G7, FreeStyle Libre 2, and FreeStyle Libre 3 are FDA-approved for use in pregnancy 1
- CGM in pregnancy should target 63-140 mg/dL (3.5-7.8 mmol/L) time-in-range 1
- Fingerstick confirmation may be necessary for hypoglycemia or hyperglycemia outside pregnancy-specific ranges 1
Patients with Chronic Kidney Disease
- Dexcom systems use modified glucose oxidase technology with improved performance at low glucose levels and reduced oxygen state impact 1
- Dexcom G6 and newer versions incorporate perm-selective membrane coating that reduces acetaminophen interference to mean 3.1 mg/dL 1
- FreeStyle Libre should be avoided in peritoneal dialysis and used cautiously in hemodialysis patients 1
Key Clinical Caveats
Substance Interference
- Salicylic acid and ascorbic acid can affect sensor accuracy by reacting with electrodes 3
- High-dose acetaminophen (>4g/day) may interfere with some older CGM systems, though newer Dexcom and FreeStyle Libre systems have reduced susceptibility 3
- Patients should be educated on potential interfering substances before CGM initiation 1