A needle-less fluid injection mechanism, including: a nozzle head for accepting a dose of fluid to be injected into the skin of a patient； a plunger that is adapted to be pushed into the nozzle to inject the dose of fluid from the nozzle； a hammer that is adapted to be thrust at and to collide with the plunger to cause the release of a first amount of fluid from the nozzle at a high pressure and then to release the rest of the fluid from the nozzle by continuing to push said plunger at a lower pressure until injecting the entire dose of fluid.
