The systems, methods, and devices described herein generally involve monitoring and/or quantification of various analyte levels in a biological fluid using one or more implantable sensors. In various aspects, systems, methods, and devices described herein can provide for the in situ calibration and/or cleaning of such sensors when implanted in the patient. The systems and devices disclosed herein can, for example, continuously or serially measure analytes within a biological fluid in vivo (e.g., without extracting the biological fluid from the patient) and periodically calibrate and/or clean the sensor without using finger sticks or additional, invasive calibration techniques. By way of non-limiting example, systems and devices disclosed herein can enable continuous monitoring of analyte concentrations (e.g., glucose) in subcutaneous interstitial fluid for several hours to a few days.