How Many Libre Monitors Are Required for 1 Year Duration?
For a full year of continuous glucose monitoring with the Freestyle Libre system, 26 sensors are required, as each sensor lasts for 14 days and must be replaced every two weeks. 1
Libre CGM System Overview
The Freestyle Libre is one of the most commonly used continuous glucose monitoring (CGM) systems, specifically categorized as an intermittently scanned CGM (isCGM) system 2. Key characteristics include:
- Each sensor lasts exactly 14 days before requiring replacement 1
- Sensors are typically applied to the back of the upper arm 1
- Unlike traditional CGM systems, the Libre doesn't require fingerstick calibration 1
- Data is obtained by scanning the sensor with a reader device rather than continuous transmission 2
Annual Supply Calculation
The calculation for annual supply is straightforward:
- 365 days per year ÷ 14 days per sensor = 26.07 sensors
- Therefore, 26 sensors are needed for a complete year of monitoring
The proper prescribing signature for Freestyle Libre reflects this usage pattern: "Freestyle Libre sensor, apply one sensor every 14 days to back of upper arm, scan as needed for glucose monitoring" 1
Usage Recommendations
For optimal clinical benefit, the American Diabetes Association recommends:
- Sensors should be worn continuously throughout the year 1
- For intermittently scanned CGM like Libre, the device should be scanned at minimum once every 8 hours to capture complete 24-hour data 2, 1
- Consistent use is associated with better clinical outcomes, including improved glycemic control and reduced hypoglycemia risk 1
Clinical Considerations
When prescribing a year's supply of Libre sensors, healthcare providers should consider:
- Patient education on proper application and scanning techniques is essential 1
- Skin reactions may occur and should be monitored 1
- The Freestyle Libre 3 has demonstrated high accuracy with an overall MARD of 7.8% compared to venous blood glucose reference 3
- Performance remains stable throughout the 14-day wear period 3
Practical Tips
- Patients should have a backup plan for glucose monitoring in case of sensor failure
- Consider prescribing an extra sensor or two beyond the calculated 26 to account for potential sensor failures or application errors
- Remind patients that each sensor must be scanned at least once every 8 hours to ensure complete data capture 2
By ensuring patients have the appropriate annual supply of 26 sensors, healthcare providers can support continuous monitoring throughout the year, which has been shown to improve glycemic control and quality of life for patients with diabetes.