Estimating glycemic variability (GV) through within-day coefficient of variation (%CVw) is recommended for patients with type 1 Diabetes (T1D). High GV (hGV) is defined as %CVw > 36%. However, continuous glucose monitoring (CGM) devices provide exclusively total CV (%CVT). We aimed to assess consequences of this disparity.


We retrospectively calculated both %CVT and %CVw of consecutive T1D patients from their CGM raw data during 14 days. Patients with hGV with %CVT >36% and %CVw ≤36% were called the “inconsistent GV group”.


A total of 104 patients were included. Mean ± SD %CVT and %CVw were 42.4 ± 8% and 37.0 ± 7.4% respectively (P < 0.0001). Using %CVT, 81 patients (73.6%) were classified as having hGV, whereas 59 (53.6%) using %CVw (P < 0.0001) corresponding to 22 patients (21%) in the inconsistent GV population.


Evaluation of GV through %CV in patients with T1D is highly dependent on the calculation method and then must be standardized.

This article contains supplementary material online at https://doi.org/10.2337/figshare.14461800.

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