Analyte sensing and response systems include a sensor detecting one or more analytes in a medium. The sensor uses decoupled transmit and receive elements or antennas to transmit a signal into the medium, and receive a response to the transmitted signal. An action that is based on the detection of the analyte is generated which can directly or indirectly affect the detected analyte in the medium. The action is automatically performed. The action can be increasing or decreasing flow from a source of the analyte, or of a chemical compound interacting with the analyte. An example of the action is controlling an insulin pump, where the analyte is glucose.