Dexcom CGM Prescription
For patients with type 1 or type 2 diabetes on intensive insulin therapy, prescribe either Dexcom G6 or G7 continuous glucose monitoring system with sensors replaced every 10 days (G6) or 10.5-15 days (G7), worn continuously on the upper arm or abdomen, with instructions to use the device daily without interruption.
Device Selection
Choose between two FDA-approved options:
- Dexcom G7: Newer generation with 8.0-9.1% MARD, 10.5-day wear (with 15.5-day version in development), no calibration required 1, 2, 3
- Dexcom G6: Established device with similar accuracy, 10-day wear, no calibration required 1, 4
Both are designated as integrated CGM (iCGM) systems approved for non-adjunctive use (meaning insulin dosing decisions can be made directly from CGM readings without fingerstick confirmation) and are compatible with automated insulin delivery systems 1.
Prescription Components
Write the prescription to include:
- Device: Dexcom G6 or G7 real-time CGM system (rtCGM)
- Sensors: Quantity sufficient for continuous use (3 sensors per month for G6, 2-3 sensors per month for G7)
- Transmitter: As needed per device specifications
- Receiver/smartphone: Compatible display device if patient doesn't have smartphone
- Duration: Ongoing with regular refills to ensure uninterrupted access 1
Patient Instructions
Critical usage parameters 1:
- Wear the device as close to daily as possible for maximal benefit
- Place sensor on upper arm or abdomen (both sites show excellent accuracy with G7: 8.2% MARD for arm, 9.1% for abdomen) 3
- Replace sensors every 10 days (G6) or 10.5 days (G7)
- No fingerstick calibrations required for treatment decisions
- Scan frequency not applicable (real-time system with continuous display)
Clinical Context
This recommendation applies specifically to:
- Type 1 diabetes: Strong evidence for A1C reduction (mean 1.0-1.3 percentage points) and improved time-in-range 1, 4
- Type 2 diabetes on intensive insulin therapy: Consistent A1C reductions and TIR improvements across multiple daily injections and basal insulin regimens 1, 5
The 2025 ADA Standards of Care explicitly recommend rtCGM devices for patients on insulin therapy, with the choice between G6 and G7 based on individual circumstances, preferences, and needs 1.
Common Pitfalls to Avoid
Supply interruptions: Ensure continuous access to sensors—gaps in CGM use diminish glycemic benefits 1. Write prescriptions with adequate refills.
Skin reactions: Assess for irritation or allergy at sensor sites and address proactively to maintain adherence 1.
Interfering substances: Educate patients about potential accuracy issues with certain medications (particularly high-dose vitamin C, acetaminophen with some systems) 1.
Temperature sensitivity: Devices have acceptable temperature ranges; readings may be affected outside these parameters 1.
Expected Outcomes
Patients using rtCGM daily achieve:
- Significant A1C reductions (0.6-1.3 percentage points depending on baseline control) 1, 4
- Increased time-in-range (70-180 mg/dL) by 8-16 percentage points 4, 5
- Reduced severe hypoglycemia rates (from 67.3 to 17.0 per 100 person-years in one study) 4
- Improved treatment satisfaction and quality of life 5, 6
The G7 system demonstrates consistent accuracy throughout the entire wear period with %20/20 agreement rates of 93-95% across all days of wear 3.