The present disclosure describes a method of detecting a drug marker in a urine sample. The drug markers are fluorophores each of which emits a unique fluorescence spectrum. Accordingly, the method does not detect the drug but rather, the drug marker. The drug marker may include quantum dots which may be functionalized by connecting the quantum dot to a biomolecule. The biomolecule may be cleavable by a peptidase, a protease, or a nuclease to release the drug. Alternatively, the composition may include a liposome carrier. A user who has consumed the drug composition provides a urine sample. The fluorescence spectrometer screens the urine for drug markers based on their unique fluorescent spectra.