Medical devices and methods for delivering therapeutic fluids transcutaneously to a body of a patient via a fluid delivery device and an adapter is provided. A Luer slip connector is provided at a first connecting end of the adapter. A therapeutic fluid container is connected with the second connecting end such that the container's neck is received in the second connecting end and a hollow penetrating member provided in the adapter punctures the septum of the container to admit the therapeutic fluid into a needle-less syringe from the container. After, fluid emerges from the tip of the penetrating member, the second connecting end of the adapter is attached to the fluid delivery device, thereby filling the reservoir with the fluid and pushing the syringe plunger forward to inject fluid into reservoir.