The present invention includes systems and methods for monitoring endogenous compound concentration in blood by detecting markers, such as odors, upon exhalation by a patient, wherein such markers are the endogenous compound itself or result from the endogenous compound. In the case of olfactory markers, the invention preferably utilizes electronic sensor technology, such as the commercial devices referred to as “artificial” or “electronic” noses or tongues, to non-invasively monitor endogenous compound levels in blood. The invention further includes a reporting system capable of tracking endogenous compound concentrations in blood (remote or proximate locations) and providing the necessary alerts with regard to emergent or harmful conditions in a patient.