FreeStyle Libre Placement Sites
The FreeStyle Libre sensor should be placed on the back of the upper arm (middle third posterior aspect) for both adults and children aged 4 years and older, as this is the only FDA-approved and clinically validated site. 1, 2
Approved Placement Site
- Upper arm placement (back of the arm): The sensor disc is designed to be worn on the posterior aspect of the upper arm for up to 14 days. 1, 2
- This site has demonstrated acceptable accuracy with a Mean Absolute Relative Difference (MARD) of 11.8% in adults. 3
- The upper arm site maintains stable accuracy throughout the 14-day wear duration. 3
Alternative Sites: Not Recommended
While some patients request alternative placement sites for cosmetic reasons, the evidence strongly argues against using other body locations:
Abdomen - Poor Performance
- The abdomen shows significantly worse accuracy with MARD of 18.5% compared to 11.8% for the arm (p = 0.002). 3
- Only 69.4% of readings fall in Clarke Error Grid Zone A (clinically acceptable range) versus 84.9% for the arm. 3
- Accuracy deteriorates markedly during week 2 of wear when placed on the abdomen. 3
- Precision between paired sensors is unacceptably poor for abdomen placement (precision absolute relative difference of 20.9% for arm/abdomen comparison versus 10.9% for arm/thigh). 3
Upper Thigh - Marginally Acceptable but Not Approved
- The upper thigh demonstrates similar accuracy to the arm (MARD 12.3% versus 11.8%, p = 0.5). 3
- Clarke Error Grid Zone A performance is comparable (84.5% for thigh versus 84.9% for arm). 3
- However, this site lacks FDA approval and manufacturer validation, making it an off-label use. 1, 2
Pediatric Considerations
- The FreeStyle Libre is approved for children aged 4 years and older, using the same upper arm placement site. 2
- Younger children and those with lower BMI may experience greater variability in accuracy (MARD inversely related to age, r = -0.266). 2
- Sensor detachment is more common in pediatric patients (43.3% reported sensor problems), requiring special attention to adhesive reinforcement. 2
Arm Selection: Right vs. Left
- Patients should rotate between right and left arms to minimize skin irritation. 4
- Be aware that statistically significant inter-arm glucose differences exist (mean difference of 3.8 mg/dL between arms, p < 0.001), though the clinical significance is debatable. 4
- Arm dominance does not explain inter-arm discordance. 4
Critical Pitfalls to Avoid
- Never place the sensor on the abdomen despite patient requests—the accuracy is clinically unacceptable and deteriorates over time. 3
- Avoid placement over scars, lipohypertrophy, or areas with skin irritation, as these compromise accuracy. 5
- Do not place sensors where clothing or activities may cause frequent bumping or premature detachment. 2
- Always maintain fingerstick blood glucose monitoring capability as backup, particularly when sensor readings seem incongruent with symptoms. 5