Provided are sensor systems and methods for detecting analytes of bodily fluids. The systems can be used to reduce the administration volume of certain compounds and/or fluids during medical monitoring or other procedures by providing a calibration path configured to receive a first fluid, a sample path isolated from the calibration path, the sample path configured to receive a bodily fluid from a subject, and a sensor apparatus comprising at least one sensor selectively positionable between the calibration path and the sample path.
