Devices and methods are provided for transdermal diagnostic sensing, alone or in combination with transdermal drug delivery. The device includes a substrate having a plurality of discrete reservoirs, each reservoir having at least one opening; contents disposed in the reservoirs, the contents of each reservoir including a diagnostic agent or a sensor for measuring an analyte; at least one discrete reservoir cap which cover said at least one opening; control means for disintegrating or permeabilizing the reservoir cap; means for transporting an analyte from the skin to said sensors and/or for transporting said diagnostic agent to the skin following release of said diagnostic agents from said reservoir; and means for securing the device to the skin of a patient.