The effect of additional mealtime insulin bolus using an insulin-to-protein ratio compared to usual carbohydrate counting on postprandial glucose in those with type 1 diabetes who usually follow a carbohydrate-restricted diet: A randomized cross-over trial.

This randomized controlled cross-over study compared postprandial glucose concentrations and incidence of hypoglycaemia for mealtime bolus insulin calculated for both meal protein and carbohydrate content, with ordinary dosing for carbohydrate content alone, in adults with type 1 diabetes who usually follow a carbohydrate-restricted diet. All 16 participants completed three test meals under each of the two conditions. The primary outcome was the time normalized Area Under the Curve (AUC) of glucose measurements. The mean (SD) AUC glucose concentration for insulin dosing for both protein and carbohydrate was 8.3 (2.1) mmol/L compared with 10.0 (2.2) mmol/L for carbohydrate alone. The difference (95% CI) was -1.76 mmol/L (-2.87 to -0.65), P = .003. The mean (SD) glucose concentration ≥ 8.0 mmol/L was 54.8 (32.4)% for dosing for protein and carbohydrate and 73.7 (26.3)% for carbohydrate alone, rate ratio (95% CI) 0.75 (0.62 to 0.89), P = .002. For glucose concentration < 4.0 mmol/L 5.5 (15.1)% and 2.8 (11.7)%; rate ratio (95% CI): 1.97 (0.90 to 4.27), P = .087. Calculating the meal insulin requirements based on the carbohydrate and protein content may have advantages over calculations based on carbohydrate alone. Further studies are required to determine how to best optimize this.