Calculating the insulin to carbohydrate ratio using the hyperinsulinaemic‐euglycaemic clamp—a novel use for a proven technique

Background In patients with type 1 diabetes, three main variables need to be assessed to optimize meal‐related insulin boluses: pre‐meal blood glucose (BG), insulin to carbohydrate ratio (I : C), and basal insulin. We are presenting data for a novel use of the hyperinsulinaemic‐euglycaemic clamp (HEC) in patients with type 1 diabetes that minimizes the impact of these variables and can be used to determine the I : C. Methods Ten subjects (six men and four women) using continuous subcutaneous insulin infusion (CSII) pumps were recruited for this study [24–65 years; BMI 27.1 ± 4.9 kg/m 2 ; A1C 7.2 ± 1.4% (mean ± SD)]. The HEC used a primed continuous intravenous insulin infusion of 40 mU/m 2 /min and a variable infusion of 20% glucose to maintain BG at 90 mg/dL. After subjects were in steady state (SS) for 50 min, a standardized meal (40% of total calories/day − 30% carbohydrate, 30% protein, 40% fat) was consumed. Subjects gave the insulin bolus with their CSII pump. No changes were made in the glucose infusion rate. Results Mean BG at SS was 85.7 ± 10.4 mg/dL. Peak BG was 115.0 ± 12.7 mg/dL at 68.5 ± 8.8 min after the meal. Mean I : C was 1 : 9.3 ± 1.7 (range 1 : 7–1 : 12). Insulin sensitivity varied from 1.9 to 9.1 mg/kg/min. Conclusions The HEC can be used to reduce confounding factors and to determine the I : C. As a first estimate of the I : C in patients with type 1 diabetes, it is recommended to start with a ratio of 1 : 9.3 and to measure post‐prandial BG at 70 min. Copyright © 2007 John Wiley & Sons, Ltd.