A medication delivery device comprising: a device body comprising an elongated pen shaped housing including a distal portion and a proximal portion , the distal portion containing a reservoir configured to hold a medicinal fluid to be dispensed through a distal outlet end of the reservoir during dose delivery; a dose setting member attached to said device body and rotatable relative to said device body about an axis of rotation during dose delivery; a sensed element attached to and rotationally fixed with said dose setting member, said sensed element including alternating first and second surface features radially-spaced about the axis of rotation of said dose setting member, the surface features facing radially; an actuator attached to said device body, said actuator being axially and rotationally fixed with said dose setting member in a first operating mode during dose setting, said actuator being non-rotatable relative to said device body in a second operating mode during dose delivery, said sensed element and said dose setting member rotating relative to said actuator during dose delivery in relation to the amount of dose delivered; a rotation sensor attached to said actuator during dose delivery, said rotation sensor including a following member attached to said actuator, the following member extending distally and including a contact surface resting against and spring-biased radially in the direction of the first and second surface features of said sensed element, the contact surface being positioned to move over the surface features during rotation of said sensed element relative to said actuator during dose delivery, said rotation sensor being responsive to the movement of the contact surface over the surface features to detect the rotation of the dose setting member; and a controller responsive to said rotation sensor to determine the amount of dose delivery based on the detected rotation of said dose setting member relative to said actuator during dose delivery. a device body comprising an elongated pen shaped housing including a distal portion and a proximal portion , the distal portion containing a reservoir configured to hold a medicinal fluid to be dispensed through a distal outlet end of the reservoir during dose delivery; a dose setting member attached to said device body and rotatable relative to said device body about an axis of rotation during dose delivery; a sensed element attached to and rotationally fixed with said dose setting member, said sensed element including alternating first and second surface features radially-spaced about the axis of rotation of said dose setting member, the surface features facing radially; an actuator attached to said device body, said actuator being axially and rotationally fixed with said dose setting member in a first operating mode during dose setting, said actuator being non-rotatable relative to said device body in a second operating mode during dose delivery, said sensed element and said dose setting member rotating relative to said actuator during dose delivery in relation to the amount of dose delivered; a rotation sensor attached to said actuator during dose delivery, said rotation sensor including a following member attached to said actuator, the following member extending distally and including a contact surface resting against and spring-biased radially in the direction of the first and second surface features of said sensed element, the contact surface being positioned to move over the surface features during rotation of said sensed element relative to said actuator during dose delivery, said rotation sensor being responsive to the movement of the contact surface over the surface features to detect the rotation of the dose setting member; and a controller responsive to said rotation sensor to determine the amount of dose delivery based on the detected rotation of said dose setting member relative to said actuator during dose delivery. <EOS>