The Vial Based Pen Injector is a novel injection device for delivering drugs from a vial. Today, drugs stored in vials are delivered using a vial-to-syringe system, whereby the user is required to withdraw and set a specific dose from the vial prior to use. This system has several problems including a high number of use steps; errors setting the correct dose; and risk of needle stick injuries. The Vial Based Pen Injector reduces the number of use steps needed to prepare a dose, while implementing features to reduce the risk of needle stick injuries and improve dose accuracy, helping healthcare professions provide a higher standard of care.