Interferent Effect of Hydroxyurea on Continuous Glucose Monitoring.

While currently available continuous glucose monitoring (CGM) systems have continually improving accuracy that has revolutionized modern diabetes care, potential medication interferences are recognized for all available CGM systems (1). For Dexcom CGM systems, hydroxyurea was recently recognized as an interfering substance that can falsely elevate sensor glucose (SG) readings (2), but the data demonstrating this interference have not been previously published. We report a patient with type 1 diabetes taking hydroxyurea who experienced falsely elevated SG values using the Dexcom G5 and G6 CGM systems, which led to the recognition of the interferent effect of hydroxyurea. A 69-year-old woman with type 1 diabetes using an insulin pump (Medtronic Paradigm Revel 723) and real-time CGM (initially Dexcom G5, then G6) took hydroxyurea (1,000 mg daily) for treatment of essential thrombocytosis. She noted that, for approximately 6 h after taking hydroxyurea, SG measurements predictably and markedly increased, even while fasting and when the time of hydroxyurea ingestion varied. In addition, the glucose management indicator (7.6%) based on 14-day average SG (170 mg/dL) was significantly higher than concomitant glycated hemoglobin (6.3%, 45 mmol/mol), suggestive of artifactual discordance. Subsequently, the patient simultaneously wore the Dexcom G6 …