What are the directions for using Dexcom (continuous glucose monitoring system) that pharmacies should provide to patients?

Pharmacy Directions for Dexcom Continuous Glucose Monitoring System

Pharmacies should dispense the Dexcom G7 rtCGM System with 3 sensors per 30-day supply (each sensor lasts 10 days), along with a receiver/display device if the patient lacks a compatible smartphone, and provide comprehensive patient education on proper use, calibration requirements, and critical contraindications. 1

Essential Prescription Components to Verify

• Specify "Dexcom G7 rtCGM System" as an integrated CGM for nonadjunctive use, allowing insulin dosing decisions without confirmatory fingerstick testing 1
• Dispense 3 sensors per 30-day period to ensure continuous monitoring coverage, with each sensor having a 10-day wear period 1
• Include the receiver/display device if documentation indicates the patient doesn't have a compatible smartphone 1
• Verify clinical justification documenting diabetes type (Type 1, Type 2 on intensive insulin, or gestational diabetes) to support medical necessity 1

Critical Patient Education Requirements

Daily Use Instructions

• Educate on daily sensor wear with no fingerstick calibration required for the Dexcom G7 system 1
• Explain the 10-day sensor lifespan and proper sensor insertion technique, typically on the abdomen, upper buttock, or posterior upper arm 2
• Instruct on the initial 12-hour warm-up period, during which readings may be less accurate 3
• Advise patients to record diet, exercise, and medication events during CGM monitoring for optimal data interpretation 3

Device Maintenance and Safety

• Warn against exposure to strong magnetic fields, MRI, conventional X-ray, and CT scanning while wearing the CGM system 3
• Clarify that mobile phone use does not affect the Dexcom device 3
• Inform about water resistance specifications for the specific Dexcom model being dispensed 3

Absolute Contraindications to Emphasize

Do NOT dispense Dexcom G7 to patients on peritoneal dialysis due to icodextrin interference with glucose oxidase-based sensors, which can cause falsely elevated readings 1, 4

Chemical Interference Warnings

• High-dose acetaminophen (>4g per day) may interfere with glucose readings 4
• Salicylic acid and ascorbic acid can affect sensor accuracy 4
• Patients in intensive care units with skin edema, vasoconstrictor drugs, hypotension, or hypoxemia may experience inaccurate results 3

Validation and Accuracy Guidance

• Instruct patients that sensor values should be within 20% of point-of-care glucose values for blood glucose concentrations >100 mg/dL to be considered valid 3
• Explain that the Dexcom G7 has a mean absolute relative difference (MARD) of approximately 10-17% compared to laboratory reference methods, with better performance after the initial days of wear 5, 6
• Advise that sensor lag time averages 5 minutes behind actual blood glucose changes, though this may be longer in dialysis patients 5, 6

Insurance Coverage Documentation

• Ensure prescription includes clinical scenarios such as unexplained severe/recurrent hypoglycemia, unexplained hyperglycemia, or dramatic glycemic variability to support insurance authorization 1
• Avoid vague orders like "CGM supplies as needed" and instead specify exact quantities to ensure insurance coverage 1
• Document that the CGM will be used >95% of the time as required by Medicare and other insurers for ongoing coverage 7

Common Dispensing Pitfalls to Avoid

• Never dispense without confirming mandatory diabetes education has been arranged or provided 1
• Do not assume all patients can use smartphone apps—verify device compatibility or include receiver 1
• Avoid dispensing to patients with severe depression or anxiety without documented additional support systems, as these patients may struggle with CGM data interpretation 1
• Ensure adequate supply overlap to prevent gaps in monitoring during sensor changes 1

Special Population Considerations

Pregnant Women with Diabetes

• Dexcom G6/G7 is accurate and safe in pregnancy with MARD of 10.3% across all trimesters 2
• Abdominal placement is acceptable in pregnant women, though posterior upper arm showed slightly better accuracy (8.7% MARD) 2

Dialysis Patients (Hemodialysis Only)

• Dexcom G7 shows acceptable accuracy in hemodialysis patients with MARD of 13.5-16.7%, though higher than non-dialysis populations 6
• Warn about greater lag times and variability in sensor performance compared to non-dialysis patients 6
• Absolute contraindication for peritoneal dialysis patients due to icodextrin interference 1, 4