Methods for monitoring subject compliance with a prescribed treatment regimen are disclosed. In one embodiment, the method comprises measuring a drug level in fluid of a subject and normalizing said measured drug level as a function of one or more parameters associated with the subject. The normalized drug level is compared to a reference value and associated confidence intervals or to a concentration range. The reference value and associated confidence intervals and/or the concentration range may be normalized based on one or more parameters associated with subjects in a reference population.
