An adjustable needleless injection system for subcutaneous injection of a liquid medication to a patient is disclosed. The adjustable needleless injection system may include: a medication cartridge that holds the liquid medication, where the medication cartridge includes a cartridge piston, a spring-actuated injector that may be coupled with the medication cartridge and configured to selectively apply force to the cartridge piston, and a charging mechanism configured to charge the spring-actuated injector based on a body type of the patient.
