OBJECTIVE: This study aimed to explore the relationship between time below range (TBR), impaired awareness of hypoglycemia (IAH), and severe hypoglycemia (SH). RESEARCH DESIGN AND METHODS: This cross-sectional study analyzed data from individuals with diabetes using continuous glucose monitors (CGMs) in the Association of British Clinical Diabetologists audit. Hypoglycemia awareness was assessed via the Gold score (≥4 denoting IAH), and SH was defined as hypoglycemia requiring third-party assistance. Logistic regression was used to determine the association between TBR percentage (<
70 mg/dL
3.9 mmol/L) at first follow-up and follow-up Gold score and SH incidence. The Youden J index identified optimal TBR percentage cutoffs for detecting IAH and SH. RESULTS: The study included 15,777 participants, with follow-up TBR and SH data available for 5,029. The median TBR percentage was 4% (interquartile range 2-6.6%), with 42% meeting the recommended TBR of ≤4%. Adjusted for age, sex, and BMI, TBR was significantly associated with SH (P <
0.002) and IAH (P = 0.005). Optimal TBR cutoffs for identifying IAH and SH were 3.35% and 3.95%, yielding negative predictive value (NPV) values of 85% and 97%, respectively. CONCLUSIONS: Our findings support the international consensus recommending a TBR of <
4% in type 1 diabetes, with high NPV values suggesting the utility of TBR in screening for SH.