T1DM patients determine their bolus insulin needs using patient and daytime specific values for carbohydrate to insulin ratio (CIR). In standard bolus calculators only the carbohydrate content of the meal is used for determining the insulin requirements, whereas newer research suggests that also fat and protein should be considered. Especially meals with a high fat content reportedly require additional insulin. A previously published method has been used to determine patient and daytime specific CIR values from recorded data (CGM profiles, bolus insulin and meal carbohydrates - no information about meal composition) of a recent clinical trial over 7 days with 40 patients. During 2 days of the trial the patients ingested a breakfast consisting almost entirely of fast absorbing carbohydrates, whereas for the other 5 days the patient could choose their breakfast composition freely, resulting in significantly higher intakes of fat and protein (high carb breakfast: 80.7% carbohydrates, 10.3% protein, 9.1% fat; average standard breakfast: 42.7% carbohydrates, 15.6% protein, 42.1% fat; % of total meal calories). Using aforementioned method the parameters of a model were adjusted to the clinical data and a patient-specific CIR was calculated from the model parameters for both, the high carb and the standard breakfasts. The identified CIR values for the high carb breakfast were typically higher than the corresponding CIRs for the standard breakfast, indicating a lower insulin requirement per gram of carbohydrates for the high carb breakfast. On average the CIR for the high carb breakfast was 14.0% higher. The difference in CIRs was found to be highly signifi cant (p=0.0008). The identified CIR values show that mixed meals require a higher amount of insulin per gram of carbohydrates than meals consisting (almost) only of carbohydrates for a correct glycemic control. The proposed method is able to adjust the insulin needs accordingly