What is the proper format for writing a prescription for a FreeStyle Libre (flash glucose monitoring system) device?

How to Write a Prescription for FreeStyle Libre Blood Glucose Monitoring Device

Write the prescription for FreeStyle Libre as a routine, ongoing supply with continuous sensor replacement every 14 days, not as a PRN or one-time order, because CGM devices must be used "as close to daily as possible for maximal benefit" and require uninterrupted access to supplies to minimize gaps in continuous glucose monitoring. 1

Essential Prescription Components

Device Specification

• Specify "FreeStyle Libre 3 System" or the specific model (FreeStyle Libre, FreeStyle Libre 2, or FreeStyle Libre 3) on the prescription 1
• Include both the sensor and reader device in the initial prescription, as the system requires pairing with a device-specific app or reader 2

Quantity and Duration

• Prescribe sensors for continuous replacement cycles: typically 2-3 sensors per month (each sensor lasts 14 days) 1, 3
• Specify the total duration of therapy (e.g., 3 months, 6 months, or ongoing) to ensure uninterrupted access 1
• Include refills to maintain continuous monitoring without gaps 1

Usage Instructions

• Direct the patient to scan the sensor at minimum once every 8 hours to capture complete 24-hour glucose data 1
• Instruct to insert the new sensor before removing the old one when changing sensors to avoid gaps in data collection 1
• Note that the device measures interstitial glucose continuously and displays data when scanned with the reading device 1

Clinical Documentation Requirements

Key Metrics to Document

• Average glucose level, percentage of time in hypoglycemia ranges, percentage of time in target range, and percentage of time in hyperglycemia range should be documented in patient records 4
• Confirm that the CGM continuously measured glucose and displayed data in real-time >95% of the time for the duration specified in the product label 4

Alert Configuration

• Document settings for real-time alerts and alarms for hypoglycemia, hyperglycemia, and rapid rates of change 4
• Ensure visual and audible alerts are properly configured for appropriate clinical response 4

Special Population Considerations

Patients with Advanced Chronic Kidney Disease

• Use FreeStyle Libre with caution in hemodialysis patients, as accuracy is reduced during dialysis sessions (MARD 18.2-22.8% during hemodialysis vs. 11.3-19.3% overall) 2
• Do NOT prescribe FreeStyle Libre for patients on peritoneal dialysis until more evidence becomes available, as there are no studies assessing whether icodextrin interferes with the sensor 2
• In hemodialysis patients, use the device to assess glucose patterns rather than focusing on specific glucose values given lower accuracy compared to other CGM systems 2
• Consider that 97.9% of readings were within clinically acceptable zones A+B on hemodialysis days in recent studies 2

Pediatric Patients

• FreeStyle Libre is approved for children aged ≥4 years 5
• Be aware of higher interindividual variability in accuracy in children, with MARD inversely related to age (younger children have higher MARD) 5
• Sensor detachment is more common in pediatric patients (43.3% reported sensor problems, mainly early detachment), requiring special attention to sensor placement and adhesive reinforcement 5

Accuracy Considerations

Sensor Age Effects

• Accuracy is lowest during the first day (MARD 14.5%) and last day (MARD 14.7%) of the 14-day sensor life, with optimal accuracy occurring on days 5-7 (MARD 7.8%) 3
• Only 1.9% of readings fall in potentially dangerous zones C, D, or E during the first day, decreasing to 0.2-0.4% during mid-life and end-of-life 3

Medication Interferences

• Document any use of high doses of acetaminophen, salicylic acid, or ascorbic acid, as these may affect sensor accuracy 4
• Note that the FreeStyle Libre uses wired-enzyme technology that is NOT susceptible to acetaminophen interference at therapeutic doses, unlike some other CGM systems 2

Common Pitfalls to Avoid

• Never prescribe as PRN or "as needed" – inconsistent use reduces clinical value and limits ability to improve quality of life and health outcomes 1
• Do not prescribe as a one-time order – these devices are designed for regular, ongoing use to monitor glucose trends over time 1
• Avoid prescribing without adequate patient education on scanning frequency (minimum every 8 hours) and sensor replacement procedures 1
• Do not rely solely on estimated HbA1c from CGM data without documenting correlation with laboratory HbA1c measurements 4
• Never fail to document instances where the CGM indicated questionable accuracy or withheld data 4

Sample Prescription Format

FreeStyle Libre 3 System

• Sensors: 2-3 sensors per month (each lasts 14 days)
• Reader device: 1 (if not using smartphone app)
• Duration: 3 months supply with refills
• Instructions: Apply new sensor every 14 days. Scan at least once every 8 hours. Insert new sensor before removing old sensor to avoid data gaps.
• Indication: Continuous glucose monitoring for diabetes mellitus management
• Refills: As needed for ongoing therapy