Molecular spectroscopy has received considerable contemporary attention for diagnosis of diabetes and cancers in various organs, including breast, skin and bladder. The present invention non-invasively detects and quantifies blood analytes, such as glucose from the tympanic membrane. This invention describes a fiber optic probe-based Raman system where the fiber probe is part of a speculum or a wearable device, e.g., headphones. The fiber optic probe can be inserted into the ear of a patient, illuminating the tympanic membrane with one or more wavelengths of light, collecting Raman scattered light by using a detector that is coupled to the fiber optic probe. The spectral data can then be processed for quantification and used to provide periodic measurements of blood analytes. This method would be appropriate as a real-time clinical adjunct for continuous monitoring of glucose and other analytes, e.g., creatinine, urea and bilirubin, in critical care patients and in neonates, where frequent blood withdrawal is particularly problematic.