Continuous glucose monitoring (CGM) systems are becoming increasingly popular for the management of type 1 diabetes mellitus (T1DM). However, one of the limitations of using CGM information for blood glucose (BG) control is the fact that the CGM sensor measures the glucose not in the blood, but in the interstitial fluid. The current paper shows how a sensor and patient-specific time delay between interstitial glucose (IG) and blood glucose (BG) can be identified from CGM recordings and BG measurements. The resulting time delay values were found to be highly patient-specific and correlated with patient characteristics. Furthermore, it was found that the CGM time delays are a good predictor for the required total daily dose (TDD) of insulin, as well as for the carbohydrate-to-insulin-ratio (CIR). Based on these findings we introduce a method of how insulin therapy in T1DM could possibly be adjusted based on identified CGM time delays.