A medical injector is disclosed. The medical injector includes an upper guard housing having a gripping component, a lower guard housing defining a reservoir, and a stopper engaged with a portion of the upper guard housing, the stopper being slidably disposed within the reservoir and sized to provide sealing engagement with an interior sidewall of the lower guard housing. The upper guard housing at least partially surrounds the lower guard housing and is moveable relative to the lower guard housing to advance the stopper through the reservoir.