A medication delivery device comprising: a housing ; a medication container having a container body to hold a medication and a slidable piston operably coupled with the container body, the slidable piston movable relative to the container body to dispense medication from the medication container, the medication container being movable relative to said housing between a storage position and a delivery position; a drive mechanism adapted to, when a dispensing event is initiated, drive the medication container from the storage position to the delivery position; and a retraction mechanism adapted to, when a retraction movement is initiated, drive the medication container from the delivery position to the storage position; characterized in that the device further comprises: an accelerometer disposed within the medication delivery device, the accelerometer configured to detect a first acceleration caused by motion of the medication container relative to the housing as the medication container is driven from the storage position to the delivery position by the drive mechanism, and configured to detect a second acceleration caused by motion of the medication container relative to the housing as the medication container is driven from the delivery position to the storage position by the retraction mechanism; and a controller operably coupled with the accelerometer, wherein the controller is configured to determine initiation of the dispensing event based on the detected first acceleration, and completion of the retraction movement based on the detected second acceleration. a housing ; a medication container having a container body to hold a medication and a slidable piston operably coupled with the container body, the slidable piston movable relative to the container body to dispense medication from the medication container, the medication container being movable relative to said housing between a storage position and a delivery position; a drive mechanism adapted to, when a dispensing event is initiated, drive the medication container from the storage position to the delivery position; and a retraction mechanism adapted to, when a retraction movement is initiated, drive the medication container from the delivery position to the storage position; characterized in that the device further comprises: an accelerometer disposed within the medication delivery device, the accelerometer configured to detect a first acceleration caused by motion of the medication container relative to the housing as the medication container is driven from the storage position to the delivery position by the drive mechanism, and configured to detect a second acceleration caused by motion of the medication container relative to the housing as the medication container is driven from the delivery position to the storage position by the retraction mechanism; and a controller operably coupled with the accelerometer, wherein the controller is configured to determine initiation of the dispensing event based on the detected first acceleration, and completion of the retraction movement based on the detected second acceleration. an accelerometer disposed within the medication delivery device, the accelerometer configured to detect a first acceleration caused by motion of the medication container relative to the housing as the medication container is driven from the storage position to the delivery position by the drive mechanism, and configured to detect a second acceleration caused by motion of the medication container relative to the housing as the medication container is driven from the delivery position to the storage position by the retraction mechanism; and a controller operably coupled with the accelerometer, wherein the controller is configured to determine initiation of the dispensing event based on the detected first acceleration, and completion of the retraction movement based on the detected second acceleration. <EOS>