To estimate the carbohydrate-to-insulin ratio (CIR), a formula dividing a constant, usually 300-500, by the total daily dose (TDD) of insulin, is widely utilized. An appropriate CIR varies for each meal of the day, however. Here, we investigate diurnal variation of CIR in hospitalized Japanese type 1 diabetic patients treated with continuous subcutaneous insulin infusion. After optimization of the insulin dose, TDD and total basal insulin dose (TBD) were 34.9 ± 10.2 and 9.3 ± 2.8 units, respectively, with a percentage of TBD to TDD of 27.3 ± 6.0%. The products of CIR and TDD at breakfast, lunch and dinner were 311 ± 63, 530 ± 161, and 396 ± 63, respectively, suggesting that in the formula estimating CIR using TDD, the constant should vary for each meal of the day, and that 300, 500, and 400 are appropriate for breakfast, lunch, and dinner, respectively.
Keywords: Carbohydrate insulin ratio; Continuous subcutaneous insulin infusion; Type 1 diabetes mellitus.