The present invention refers to an injection device comprising a housing (5) with a receptacle (2) for the product, a dosing mechanism for setting a product dosage to be administered and for displaying the set product dosage and a dispensing mechanism for dispensing the product. The dispensing mechanism may comprise a piston rod (8), which is moveable relative to the housing (5) in a dispensing direction in order to eject the set product dosage in a dispensing stroke corresponding to the set product dosage, and a spring (7b), which is arranged such that the length of the spring (7b) changes during ejecting the set product dosage. The device further comprises a first detector (21) for detecting a change in the length of the spring (7b) and a feedback generator mechanism (20) connected to the first detector (21) for generating a feedback responsive to signals received from the first detector (21).
