An apparatus and method perform non-invasive lithium measurement of a patient wherein an apparatus comprising a permanent magnet, and at least one radiofrequency coil tuned to the resonant frequency of one or more isotopes of lithium are coupled to a cavity less than 5 cm in diameter in which a subjects body part (other than the subjects brain) can be inserted, wherein, the concentration of lithium in the subjects body is assessed based on one or more measurements of an amount of lithium detected in the body part without the need for withdrawing fluids from the body.
