In one embodiment, a miniaturized wearable nuclear magnetic resonance (NMR) apparatus is described. The example NMR apparatus accesses data (e.g., table, mathematical expression) that describes a relation between a nuclear magnetic resonance (NMR) signal decay rate and a known concentration of glucose in a fluid. The NMR apparatus acquires, non-invasively and in-vivo, an observed NMR signal decay rate from a fluid in a patient, and estimates a concentration of glucose in the fluid in the patient by comparing the observed NMR signal decay rate with the data that describes the relation between the NMR signal decay rate and the known concentration of glucose. The data may be generic to a population and a class of devices or may be customized to an individual patient and an individual device.
