Embodiments of the present disclosure are directed to systems, devices/apparatuses and methods for assessing a residual insulin value for a user/patient. Such embodiments may be implemented by selecting a first value corresponding to a duration of insulin action； selecting a second value corresponding to a lock out time duration, selecting a first time period beginning at a time point T0 minus the first value and ending at the time point T0 minus the second value, selecting one or more boluses delivered during the first time period； for each of the one or more boluses selecting a corresponding residual insulin value estimated at the time point T0, computing the cumulative residual insulin value by summation of the corresponding residual insulin values.
