A computer-implemented method for providing a personalized tool for estimating 1,5-anhydroglucitol is provided. An electronically-stored history of empirically measured glucose levels is maintained for a patient over a set period of time in order of increasing age. A predictive model of estimated glycated hemoglobin is built on a computer workstation. A decay factor is designated particularized to the patient. The decay factor is applied to each of the measured glucose levels. The measured glucose levels is scaled by a scaling coefficient. The measured glucose levels are aggregated and scaled as decayed and scaled into an estimate of glycated hemoglobin for the time period. The glycated hemoglobin estimate is displayed to the patient on the computer workstation.