Therapeutic drug monitoring (TDM) is a branch of clinical chemistry that specializes in the measurement of medication levels in serum. TDM requires that the laboratory make quantitative measurements of drugs and/or their metabolites. These measurements are made using patient serum samples. TDM can be contrasted with urine drug testing. While both measure drugs in patient specimens, urine drug testing is performed to detect drug abuse or confirm patient compliance when a patient is prescribed a drug with high abuse potential. Determining actual drug concentrations are less important in urine drugs of abuse screening. On the other hand, providing accurate, quantitative, concentrations of drugs is essential for TDM. Serum concentrations provided with TDM testing allow clinicians to adjust medication dosages as well as assess a patient's drug metabolism response and their compliance or dosing regimen.
