A method for calibrating a handheld diabetes managing device based on data generated by a continuous glucose monitor. The method can include sampling a current of the continuous glucose monitor at a sampling interval over a time period to generate a plurality of current samples for the time period. The method can also include determining a mean, median and standard deviation of the plurality of current samples. The blood glucose level of the patient can be measured at a first time and a calibration equation that associates the plurality of current samples with the estimated glucose level of the patient based on the measured blood glucose level and the plurality of current samples can be determined when the standard deviation is less than a first threshold and an absolute value of a difference between the mean and median is less than a second threshold.
