Auto-injector for administering a dose of a liquid medicament, comprising: - a body arranged to contain a syringe with a hollow injection needle and a stopper for sealing the syringe and displacing the medicament, the body having a distal end and a proximal end with an orifice intended to be applied against an injection site, wherein the syringe is slidably arranged with respect to the body, - a torsion spring capable of, upon activation: - pushing the needle from a covered position inside the body into an advanced position through the orifice and past the proximal end, - operating the syringe to supply the dose of medicament, and - activating means arranged to lock the spring means in a pressurized state prior to manual operation and capable of, upon manual operation, releasing the spring means for injection, wherein the torsion spring is grounded at one end (11.1) in the body and at the other end (11.2) in a first gear member rotatable about a longitudinal axis, wherein the first gear member, upon rotation, is arranged for translating a second gear member toward the proximal end, the second gear member prevented from rotating and arranged to be coupled to the stopper in order to push it towards the proximal end, wherein the first gear member is engaged with the activating means prior to manual operation in a manner to prevent rotation and disengaged from the activating means upon manual operation, wherein a ratchet wheel is arranged on the first gear member, the ratchet wheel having a number of circumferentially arranged teeth (12.1), wherein the activating means comprise at least one locking feature (15, 10.2) for engaging the ratchet wheel in a manner to prevent rotation and wherein the locking feature (15, 10.2) is arranged to allow rotation on manual operation, characterized in that in order to insert the hollow needle and to inject the dose the second gear member is coupled to the stopper by a plunger (22, 23) which is releasably engageable with the second gear member for joint axial movement, wherein the plunger (22, 23) is disengageable from the second gear member upon the second gear member reaching its maximum proximal position in order to allow the syringe to be retracted after injection, wherein a retraction slider tube is arranged in a proximal part of the body in a manner to be prevented from rotation and wherein at least one latch for restricting axial translation of the retraction slider tube is provided in the body, the latch being disengageable by at least one ramp feature on the second gear member when the second gear member is in or near a maximum proximal position, wherein the retraction slider tube comprises at least one dog feature for retracting the syringe when the retraction slider tube is retracted by the first gear member. - a body arranged to contain a syringe with a hollow injection needle and a stopper for sealing the syringe and displacing the medicament, the body having a distal end and a proximal end with an orifice intended to be applied against an injection site, wherein the syringe is slidably arranged with respect to the body, - a torsion spring capable of, upon activation: - pushing the needle from a covered position inside the body into an advanced position through the orifice and past the proximal end, - operating the syringe to supply the dose of medicament, and - pushing the needle from a covered position inside the body into an advanced position through the orifice and past the proximal end, - operating the syringe to supply the dose of medicament, and - activating means arranged to lock the spring means in a pressurized state prior to manual operation and capable of, upon manual operation, releasing the spring means for injection,