Aim: To determine the sensor performance of the Abbott Freestyle® Libre iCGMS during glycemic challenges and acute exercise during multiple 23-hours inpatient phases.

Methods: 17 people with T1D (4 women, age 34.9 ± 15.5 years, BMI 25.9 ± 3.0 kg/m2, HbA1c 7.3 ± 1.4% (56 ± 15 mmol/mol)) on multiple daily injections were included in the study, consisting of four 23-hours inpatient phases with meal-induced glycemic disturbances and 45-minutes moderate-intensity cycle ergometer exercises. iCGMS was compared to reference blood glucose by median absolute relative difference (MARD), Clarke Error Grid (CEG) and Bland-Altman (intention-to-treat).

Results: The overall MARD (IQR) during the inpatient phases (excluding exercise) was 12.9% (6.1-21.5%), during hypoglycemia 31.6% (14.0-46.8%), euglycemia 14.5% (7.0-22.5%) and hyperglycemia 8.7% (4.6-14.6%). The overall Bland-Altman analysis showed a bias (95% LoA) of 19.8 mg/dL (-78.37-118 mg/dL) and CEG is illustrated in the Figure. The overall MARD during exercise was 29.8% (17.5-39.8%), during hypoglycemia 45.1% (35.2-51.1%), euglycemia 30.7% (18.7-39.2%) and hyperglycemia 16.3% (10.0-22.8%).

Conclusion: iCGMS interstitial glucose readings should be used cautiously during hypoglycemia and exercise and need confirmatory blood glucose measurements.


O. Moser: Research Support; Self; Abbott, Dexcom, Inc., Novo Nordisk A/S. M.L. Eckstein: Research Support; Self; Novo Nordisk A/S. O. McCarthy: None. R. Deere: None. J. Pitt: None. D.M. Williams: None. J. Hayes: None. S.C. Bain: Advisory Panel; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, Merck Sharp & Dohme Corp., Mylan, NAPP Pharmaceuticals Limited, Novo Nordisk A/S, Sanofi. R.M. Bracken: None.


Novo Nordisk A/S

Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. More information is available at