Auto-injector for administering a dose of a liquid medicament, comprising: - a tubular chassis telescopable in a tubular case, - a carrier subassembly comprising a tubular carrier slidably arranged relative to the chassis inside the case, the carrier adapted to contain a syringe with a hollow injection needle, a drive spring and a plunger for forwarding load of the drive spring to a stopper of the syringe, wherein the syringe is lockable for joint axial translation with the carrier, - a trigger button arranged distally or laterally in or on the case, - a control spring arranged around the carrier, - a plunger release mechanism arranged for releasing the plunger for expelling the medicament when the carrier has at least almost reached an extended proximal position, characterized in that the auto-injector further comprises: - a needle extension control mechanism for coupling a proximal end of the control spring to either the carrier for advancing it for needle extension or to the chassis for needle retraction depending on the relative axial position of the carrier and the chassis, - a detent mechanism arranged for coupling the chassis to the carrier for joint axial translation relative to the case, wherein the detent mechanism is arranged to decouple the chassis from the carrier upon actuation of the trigger button thus allowing the carrier to move relative to the chassis so as to cause the needle extension control mechanism to switch the proximal end of the control spring to the carrier for needle extension, - a syringe retraction control mechanism arranged for coupling a distal end of the control spring to either the carrier for needle retraction or to the case otherwise. - a tubular chassis telescopable in a tubular case, - a carrier subassembly comprising a tubular carrier slidably arranged relative to the chassis inside the case, the carrier adapted to contain a syringe with a hollow injection needle, a drive spring and a plunger for forwarding load of the drive spring to a stopper of the syringe, wherein the syringe is lockable for joint axial translation with the carrier, - a trigger button arranged distally or laterally in or on the case, - a control spring arranged around the carrier, - a plunger release mechanism arranged for releasing the plunger for expelling the medicament when the carrier has at least almost reached an extended proximal position, characterized in that the auto-injector further comprises: - a needle extension control mechanism for coupling a proximal end of the control spring to either the carrier for advancing it for needle extension or to the chassis for needle retraction depending on the relative axial position of the carrier and the chassis, - a detent mechanism arranged for coupling the chassis to the carrier for joint axial translation relative to the case, wherein the detent mechanism is arranged to decouple the chassis from the carrier upon actuation of the trigger button thus allowing the carrier to move relative to the chassis so as to cause the needle extension control mechanism to switch the proximal end of the control spring to the carrier for needle extension, - a syringe retraction control mechanism arranged for coupling a distal end of the control spring to either the carrier for needle retraction or to the case otherwise.