Medical device for sensing glucose

Medical devices, utilizing multiple reservoirs to protect and selectively expose sensors or other reservoir contents, are provided having (i) a reservoir contents destruction mechanism to interrupt the release or exposure of reservoir contents, for example, to deactivate an unneeded sensor and prevent it from negatively impacting other sensors, (ii) a protective covering material layer over the sensor underneath the reservoir cap, which protects the sensor membrane and sensor during reservoir cap disintegration and then is removed, (iii) a device design for containing sensors in shallow, wide reservoir structures to enhance sensor exposure by minimizing molecular diffusion distances, (iv) an implantable sensor unit and a separate drug delivery unit, or (v) combinations thereof.