This disclosure describes, among other features, systems and methods for customizing calibration curves, parameter algorithms, and the like to individual users. An initial calibration curve generated based on a population can be used as a starting point in an algorithm for measuring a physiological parameter such as glucose. The measurement algorithm can determine one or more initial measurement values for a user based on the initial calibration curve. In certain embodiments, one or more alternative measurements, such as invasive or minimally invasive measurements, can periodically or sporadically be input into the measurement algorithm. The algorithm can use the alternative measurements to adapt the calibration curve to the individual. As a result, measurements for the individual can more accurately reflect the individual's actual parameter values.