Methods, systems and devices for assessing residual insulin time of a patient are provided. In one embodiment, the method and the device can be implemented by receiving a confirmation that an insulin dose has been administered to the patient； repetitively receiving a value corresponding to the patient's blood glucose level； identifying at least two consecutively received values based on a predetermined criteria； and, selecting the residual insulin time corresponding to a time period between the confirmation that the insulin dose has been administered and a time corresponding to the identification of the at least two consecutively received values.
