A glucose monitoring system for monitoring a glucose level in a user, comprising: (a) a continuous glucose monitoring device configured to monitor glucose levels in the user's interstitial fluids and to generate a CGM time series representative thereof; (b) a blood glucose data source configured to generate BG references representative of the user's blood glucose levels at discrete time intervals; (c) a data preprocessing module, responsive to the CGM time series and to the blood glucose data, configured to detect outliers and artifacts in both the CGM time series and the BG references and configured to generate a preprocessed CGM signal corresponding to the CGM time series from which any outliers and artifacts are discarded and to generate a preprocessed BG signal corresponding to the BG references from which any outliers and artifacts are discarded; (d) a retrospective CGM calibration module, responsive to the preprocessed CGM signal and the preprocessed BG signal, configured to perform a retrospective calibration of the preprocessed CGM signal to compensate for systematic underestimation and overestimation of CGM time series with respect to reference BG values due to: blood-to-interstitial glucose kinetics, sensor drift, errors in CGM sensor calibration, and changes in sensor sensitivity, the retrospective CGM calibration module also configured to generate a retrospectively calibrated CGM signal representative thereof by rescaling the calibrated CGM signal so as to stay within a confidence interval of the BG values; characterised in that the glucose monitoring system further comprises (e) a constrained inverse problem solver module, responsive to the retrospectively calibrated CGM signal, configured to: deconvolute the retrospectively calibrated CGM signal based on a model of blood-to-interstitial glucose kinetics, define a confidence range of the preprocessed BG signal, wherein the confidence range is within a predetermined confidence interval of the preprocessed BG signal; generate a retrofitted glucose concentration profile with the confidence range of the preprocessed BG signal, wherein the retrofitted glucose concentration profile is constrained to pass within the confidence range. (a) a continuous glucose monitoring device configured to monitor glucose levels in the user's interstitial fluids and to generate a CGM time series representative thereof; (b) a blood glucose data source configured to generate BG references representative of the user's blood glucose levels at discrete time intervals; (c) a data preprocessing module, responsive to the CGM time series and to the blood glucose data, configured to detect outliers and artifacts in both the CGM time series and the BG references and configured to generate a preprocessed CGM signal corresponding to the CGM time series from which any outliers and artifacts are discarded and to generate a preprocessed BG signal corresponding to the BG references from which any outliers and artifacts are discarded; (d) a retrospective CGM calibration module, responsive to the preprocessed CGM signal and the preprocessed BG signal, configured to perform a retrospective calibration of the preprocessed CGM signal to compensate for systematic underestimation and overestimation of CGM time series with respect to reference BG values due to: blood-to-interstitial glucose kinetics, sensor drift, errors in CGM sensor calibration, and changes in sensor sensitivity, the retrospective CGM calibration module also configured to generate a retrospectively calibrated CGM signal representative thereof by rescaling the calibrated CGM signal so as to stay within a confidence interval of the BG values; characterised in that the glucose monitoring system further comprises (e) a constrained inverse problem solver module, responsive to the retrospectively calibrated CGM signal, configured to: deconvolute the retrospectively calibrated CGM signal based on a model of blood-to-interstitial glucose kinetics, define a confidence range of the preprocessed BG signal, wherein the confidence range is within a predetermined confidence interval of the preprocessed BG signal; generate a retrofitted glucose concentration profile with the confidence range of the preprocessed BG signal, wherein the retrofitted glucose concentration profile is constrained to pass within the confidence range. deconvolute the retrospectively calibrated CGM signal based on a model of blood-to-interstitial glucose kinetics, define a confidence range of the preprocessed BG signal, wherein the confidence range is within a predetermined confidence interval of the preprocessed BG signal; generate a retrofitted glucose concentration profile with the confidence range of the preprocessed BG signal, wherein the retrofitted glucose concentration profile is constrained to pass within the confidence range.