The invention relates to a torsion spring driven injection device for ejecting set doses of a liquid drug. In a first aspect the torsion spring driven injection device is provided with a blocking structure which is operated by the rotatable display element such that the set dose can only be expelled when a certain minimum dose size has been set. In a second aspect the torsion spring driven injection device is provided with a release mechanism which secures that the set dose can only be expelled as one single full dose in one stroke. The two aspects can easily be combined such that the predetermined minimum dose size most be expelled as one single dose.