Benefits of real-time continuous glucose monitoring in adults with type 1 diabetes


Dr Sanjay Kalra, DM (AIIMS); President-elect, SAFES, Bharti Hospital, Karnal, India; Dr Ashok Kumar, Dept. of Endocrinology, Cedar Clinic, Panipat, Haryana, India    20 February 2023

Shifting from intermittently scanned to real-time continuous glucose monitoring in adult patients with type 1 diabetes significantly improved glycemic outcomes. These beneficial effects persisted for the duration of the trial, according to the 24-month results from the randomized ALERTT1 trial published in The Lancet Diabetes & Endocrinology.1


This study was conducted at six hospitals in Belgium and involved 254 adults aged ≥18 years with type 1 diabetes. All of them had been on intermittently scanned continuous glucose monitoring (isCGM). For this study, 127 subjects were randomized to real-time continuous glucose monitoring (rtCGM) with alerts (intervention group) and an equal number of participants continued with isCGM without alerts (control group). At the end of 6 months, 119 of the control group were shifted to rtCGM (is-rtCGM group), while 123 in the intervention group continued with rtCGM (rt-rtCGM group, n=123).


Changes in the time in range (70-180 mg/dL) was the primary outcome of the 24-month extension trial, while changes in HbA1c, time in clinically significant hypoglycemia (<54 mg/dL) and Hypoglycemia Fear Survey worry (HFS-worry) score were the major secondary outcomes.


In the is-rtCGM group, the time in range increased from 51.8% at 6 months when participants switched to rtCGM to 63.5% at one year and remained steady up to 24 months showing a change of 11.7 percentage points. It increased from 52.5% at baseline in the rt-rtCGM group to 63.0% at one year. This also remained stable for 2 years showing a change of 10.7 percentage points.


In the is-rtCGM group, HbA1c declined from 7·4% at 6 months to 6.9% at 24 months. In the rt-rtCGM group, HbA1c decreased from 7.4% at the start of the study (month 0) to 7.0% at 24 months.


“The change in HFS-worry score was -2·67 (month 24 vs month 6; p=0·0008) in the is-rtCGM group and -5·17 points (month 24 vs month 0; p<0·0001) in the rt-rtCGM group.” Severe hypoglycemia episodes reduced from 31.0 to 3.3 per 100 patient-years after changing over to rtCGM. No between-group difference was observed for time in clinically significant hypoglycemia after 12 months.


In this study, a marked improvement in time in range was noted among those who received rtCGM including those who switched over to rtCGM from isCGM. The improvement remained stable up to 24 months of the trial period in both groups. A significant difference was noted in worry about hypoglycemia after switching from isCGM without alerts to rtCGM with alerts. These findings support the use of rtCGM in adult patients with type 1 diabetes.




  1. Visser MM, et al. Effect of switching from intermittently scanned to real-time continuous glucose monitoring in adults with type 1 diabetes: 24-month results from the randomised ALERTT1 trial. Lancet Diabetes Endocrinol. 2023 Feb;11(2):96-108. doi: 10.1016/S2213-8587(22)00352-7.

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