Despite recent progress in insulin delivery, carbohydrate counting is essential for determining prandial insulin doses and is, therefore, a key component of education for patients living with type 1 diabetes (PwT1D). This study aimed to evaluate the relationship between carbohydrate knowledge and glycemic control.

Carbohydrate knowledge was assessed using GluciQuizz, a validated, self-administered questionnaire totaling 36 points submitted to participants in the SFDT1 cohort. Glycemic control was determined using a 14-day time in range (TIR, 70–180 mg/dl)

The median age of the 635 participants was 43 [interquartile range 32–54] years, T1D duration of 25 [14–36] years. The median overall GluciQuizz score was 25 [23–28]: 24 [21–27] among the 158 participants treated with multiple daily injections (MDI), 25 [22–27] among the 255 users of continuous subcutaneous insulin infusion (CSII), and 26 [24–29] among the 222 users of automated insulin delivery (AID) systems. Median TIR (%) was: overall 68 [55–77]; MDI 60 [50–72]; CSII 62 [49–73]; AID 75 [69–82].

The total GluciQuizz score was positively associated with TIR in the overall population (β ± SE = 0.04 ± 0.01; P < 0.001). This association remained significant in CSII users (β ± SE = 0.06 ± 0.02; P < 0.001) but not in those treated with MDI ( P = 0.19) or AID ( P = 0.55).

Better carbohydrate knowledge is independently associated with improved glycemic control in PwT1D using CSII but not among those using MDI or AID systems. These findings highlight the continued relevance of structured nutritional education, particularly for individuals using CSII.