Adjustable volume syringes and systems are disclosed. An adjustable volume syringe includes a delivery syringe barrel, a reservoir syringe barrel positioned at least partially within the delivery syringe barrel, and a reservoir plunger positioned at least partially within the reservoir syringe barrel. The delivery syringe barrel is configured to contain a first amount of a fluid. The reservoir syringe barrel is configured to contain a second amount of the fluid. A system includes the adjustable volume syringe, a dispensing module in communication with the syringe, and a processor in communication with the dispensing module. The processor may be configured to determine an administration amount of the fluid in the adjustable volume syringe, and transmit signals causing the dispensing module to adjust the volume of fluid in the syringe to the administration amount and deliver the administration amount by moving the reservoir syringe barrel with respect to the delivery syringe barrel.