AbstractAimsWe sought to assess whether conversion from Freestyle Libre to Freestyle Libre 2 (with low and high glucose alert functions) was associated with improved glucose metrics.Research Design and MethodsA prospective observational study to assess changes in CGM metrics in 672 adults with type 1 diabetes when converting to Freestyle Libre 2. Secondary outcomes included predictors of reduction in time below range (TBR) and increase in time in range (TIR).ResultsTBR fell by a median of 1.0% (IQR −2.7 to 0.3, p < 0.001) after 12 months and TIR decreased by 1.0% (−8.7 to 6.0, p = 0.004). TIR did not fall in people using high glucose alerts (p = 0.353). Average duration of low glucose events (<3.9 mmoL/L) fell by 10 min (−46 to 18, p < 0.001). Significant improvements in TIR (p = 0.029) and time above 13.9 mM (p = 0.002) were observed in those using high glucose alerts. Alert threshold settings were not associated with glycaemic response; however, low alert use was independently associated with a fall in TBR of ≥0.5% (HR 1.9 [95% CI 1.2–3.1], p = 0.009) and high alert use was independently associated with a rise in TIR of ≥5% (HR 1.6 [95% CI 1.0–2.5], p = 0.043) at 12 months.ConclusionsConversion to Freestyle Libre 2 was associated with significant improvements in low glucose metrics. Alert function users were more likely to see improvements across all CGM metrics. Challenges remain in encouraging alert use, helping users set optimal alert thresholds and optimizing response to alerts.