Effectiveness of Continuous Glucose Monitoring for Glycemic Outcomes in Adults with Type 1 and Type 2 Diabetes

Abstract

Continuous glucose monitoring (CGM) generates ambulatory glucose data that complement glycated haemoglobin (HbA1c) and capillary blood glucose monitoring by characterising glucose exposure, variability, and hypoglycemia. We systematically reviewed comparative studies of personal CGM in adults with type 1 or type 2 diabetes published from 2019 through October 2026. Randomised trials and comparative cohort studies were eligible when they evaluated real-time CGM (rtCGM), intermittently scanned CGM (isCGM), or flash glucose monitoring against self-monitoring of blood glucose, routine care, or another CGM modality and reported HbA1c, time in range (TIR), time below range (TBR), hypoglycemia, hyperglycemia, or glycemic variability. Pediatric-only, pregnancy-only, inpatient-only, accuracy-only, non-comparative studies, and automated insulin-delivery studies in which an independent CGM effect could not be isolated were excluded. Results were synthesised by diabetes type, insulin regimen, CGM strategy, comparator, and outcome because clinical and methodological diversity precluded a clinically meaningful pooled estimate. In type 1 diabetes, personal CGM compared with blood glucose monitoring reduced hypoglycemic exposure and modestly improved HbA1c in older adults. Among adults already using isCGM, switching to rtCGM improved TIR, HbA1c, and TBR over six months. In type 2 diabetes, personal CGM improved HbA1c and/or TIR among adults treated without insulin, with basal insulin, or with multiple daily injections; however, the magnitude and attribution of benefit depended on whether structured education or additional clinical support was part of the intervention. Findings for episodic and professional monitoring were less consistent and address different clinical strategies from sustained personal monitoring. Personal CGM is associated with clinically relevant improvements in glycemic outcomes in adults, particularly when the monitoring modality, insulin regimen, patient education, and follow-up support are aligned with the clinical objective.