Assessing Time Below Range as a Predictor of Severe Hypoglycemia: Insights From Six Clinical Trials

What is it about?

People with type 1 diabetes often wear continuous glucose monitors (CGMs) that measure glucose every few minutes. We asked whether a person’s amount of time spent in low glucose levels before a trial (called “time below range,” or TBR) could predict who would later have a severe hypoglycemia event (a very low blood sugar requiring help). We combined baseline CGM data from six clinical trials (1,433 participants) and found that people who later had severe hypoglycemia tended to spend slightly more time below 70 mg/dL and 54 mg/dL at baseline. However, baseline TBR alone did not accurately identify who would experience severe episodes: no single cutoff gave both high sensitivity and high specificity. Short follow-up periods (3–6 months) and few events limited prediction further. In plain terms: baseline CGM information helps rule out low risk but is not enough by itself to reliably predict severe hypoglycemia. Better prediction will require combining CGM measures with clinical and behavioral information and longer-term monitoring.

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