A jet injector (10,86), comprising: a prefilled syringe (18,88) comprising: a container portion defining a fluid chamber (22,106) containing a fluid medicament; an injection-assisting needle disposed at a distal end of the fluid chamber (22,106), having an injecting tip configured for piercing an insertion location, and defining a fluid pathway in fluid communication with the fluid chamber for injecting the fluid medicament from the fluid chamber (22,106) into an injection site; a plunger (28,104) movable within the fluid chamber (22,106); and a housing (12,108) that houses the prefilled syringe (18,88) and is configured for allowing insertion of the injection-assisting needle at the insertion location to an insertion point that is at a penetration depth below a surface at the insertion location; a syringe support supportively mounting the prefilled syringe (18,88) to the housing (12,108); and an energy source configured for biasing the plunger (28,104) with a force selected to produce an injecting pressure in the fluid medicament in the fluid chamber (22,106) that substantially remains between about 5,5 Bar (80 p.s.i.) and 68,9 Bar (1000 p.s.i.) during injection of the fluid medicament to jet inject the fluid medicament from the fluid chamber through the injection-assisting needle to the injection site, characterized in that the prefilled syringe (18,88) further comprises a syringe body (36,120) that includes a flange and a wall and a needle hub portion of unitary construction, and the injection-assisting needle is mounted to the needle hub portion. a prefilled syringe (18,88) comprising: a container portion defining a fluid chamber (22,106) containing a fluid medicament; an injection-assisting needle disposed at a distal end of the fluid chamber (22,106), having an injecting tip configured for piercing an insertion location, and defining a fluid pathway in fluid communication with the fluid chamber for injecting the fluid medicament from the fluid chamber (22,106) into an injection site; a plunger (28,104) movable within the fluid chamber (22,106); and a container portion defining a fluid chamber (22,106) containing a fluid medicament; an injection-assisting needle disposed at a distal end of the fluid chamber (22,106), having an injecting tip configured for piercing an insertion location, and defining a fluid pathway in fluid communication with the fluid chamber for injecting the fluid medicament from the fluid chamber (22,106) into an injection site; a plunger (28,104) movable within the fluid chamber (22,106); and a housing (12,108) that houses the prefilled syringe (18,88) and is configured for allowing insertion of the injection-assisting needle at the insertion location to an insertion point that is at a penetration depth below a surface at the insertion location; a syringe support supportively mounting the prefilled syringe (18,88) to the housing (12,108); and an energy source configured for biasing the plunger (28,104) with a force selected to produce an injecting pressure in the fluid medicament in the fluid chamber (22,106) that substantially remains between about 5,5 Bar (80 p.s.i.) and 68,9 Bar (1000 p.s.i.) during injection of the fluid medicament to jet inject the fluid medicament from the fluid chamber through the injection-assisting needle to the injection site,