A spring-loaded medical injection device for automatically ejecting set doses of a drug, comprising: a housing having a proximal end carrying an injection button and an opposite distal end carrying an injection needle, the injection button movable in the distal direction against the bias of a return spring, and movable proximally by the force of the return spring, a rotatable dose setting member coupled to the housing for straining an injection spring when setting the size of the dose to be injected, an axially movable release element for releasing the strained injection spring to drive a driver thereby ejecting the set dose, which release element is axially movable from a first position to a second position by the injection button and movable from the second position back to the first position by the force of the return spring, the device characterized in that the return spring urging the injection button in the distal direction is a polymeric spring, and in that the device further comprises a plurality of radially movable fingers (31, 15) which releasable couple the injection button and the release element and which fingers (31, 15) are provided either integral with the injection button or integral with the release element, and which fingers in the first position are in a radial disengaged position wherein the injection button is disengaged from the release element allowing the injection button to move axially independently of the release element, and which fingers in the second position are in a radial engaged position wherein the injection button engages with the release element such that the injection button moves axially together with the release element, wherein at least a part of the release element and a part of the injection button is axially guided in a channel provided in the dose setting member or in the housing and having an internal diameter, and wherein a radially outer edge (16, 32) of the plurality of fingers (15, 31) defines an external diameter greater that the internal diameter of the channel, such that the fingers (15, 31) in the first position are in their disengaged position outside the channel and in the second position are squeezed inside the channel. a housing having a proximal end carrying an injection button and an opposite distal end carrying an injection needle, the injection button movable in the distal direction against the bias of a return spring, and movable proximally by the force of the return spring, a rotatable dose setting member coupled to the housing for straining an injection spring when setting the size of the dose to be injected, an axially movable release element for releasing the strained injection spring to drive a driver thereby ejecting the set dose, which release element is axially movable from a first position to a second position by the injection button and movable from the second position back to the first position by the force of the return spring, the device characterized in that the return spring urging the injection button in the distal direction is a polymeric spring, and in that the device further comprises a plurality of radially movable fingers (31, 15) which releasable couple the injection button and the release element and which fingers (31, 15) are provided either integral with the injection button or integral with the release element, and which fingers in the first position are in a radial disengaged position wherein the injection button is disengaged from the release element allowing the injection button to move axially independently of the release element, and wherein at least a part of the release element and a part of the injection button is axially guided in a channel provided in the dose setting member or in the housing and having an internal diameter, and wherein a radially outer edge (16, 32) of the plurality of fingers (15, 31) defines an external diameter greater that the internal diameter of the channel, such that the fingers (15, 31) in the first position are in their disengaged position outside the channel and in the second position are squeezed inside the channel.