Hand-held injection devices and methods of use

At least one hand-held injection device for the metered injection of a liquid drug into a person's tissue is disclosed. The exemplary injection device comprises an elongated drug reservoir having a longitudinal reservoir axis (A), an elongated dosing unit having a dosing unit inlet, a dosing unit outlet, and a metering cavity, the dosing unit having a longitudinal dosing unit axis (A′), the elongated drug reservoir being fluidically coupled to the dosing unit inlet. The dosing unit and the drug reservoir are arranged such that the longitudinal dosing unit axis (A′) is in parallel alignment with the reservoir axis (A). The dosing unit structured to allow the flow of the liquid drug from the drug reservoir into the metering cavity via the dosing unit inlet, thus charging the metering cavity, and to subsequently discharge the metering cavity by dosing drug out of the metering cavity into the dosing unit outlet.