In one aspect, an apparatus for monitoring a physiological condition of a patient is disclosed. The apparatus includes a body having an attachment portion configured to be inserted into the skin of a patient to affix the body to the patient. The apparatus includes a sensor coupled to the body that is configured to generate sensor data corresponding to a physiological condition of the patient when the body is secured to the skin of the patient. The apparatus further includes a reference sensor that is remote from the sensor coupled to the body and is configured to engage an outer surface of skin to generate reference data against which the sensor data is compared.