Cannabinoids, the main constituents of Cannabis, are a class of highly abused compounds of which, Δ-9-tetrahydrocannabinol (THC) is the primary psychoactive molecule. Despite the wide use of THC, its metabolism in humans is still in need of greater understanding. THC is metabolized to 11-OH-THC and sequentially to 11-COOH-THC by cytochrome P450 enzymes (CYPs) 2C9 and 2C19. 11-COOH-THC is then further conjugated to form 11-COOH-THC-glucuronide by UDP-glucuronosyltransferases (UGTs) 1A1 and 1A3. THC and its subsequent metabolites have been shown to bind to liver-type fatty acid binding protein (FABP1). FABPs are intracellular lipid binding proteins (iLBPs) that regulate the homeostasis of their endogenous ligands by solubilizing these hydrophobic compounds in the cytosol. Knockout of FABP1 in mouse hepatocytes was shown to decrease the formation and clearance of 11-OH-THC while the metabolism of 11-COOH-THC appeared to be unaffected. The goal of the current investigation is to translate these results into the human liver. Previously, our lab expressed and purified human FABPs to test their effect on THC metabolism in incubation assays with human liver microsomes (HLMs) and recombinant enzymes. After initiating the THC reaction with the CYP cofactor, NADPH, the 11-OH-THC product was extracted and quantified using LC-MS/MS. We found that both FABP and albumin changed the metabolic rate of THC in an enzyme specific manner. Because 11-OH-THC formation was altered in the presence of FABPs compared to the HSA control, we extend this method to continue our investigation with 11-COOH-THC metabolism. Considering that UGTs are on the luminal rather than the cytosolic side of the endoplasmic reticulum and that 11-COOH-THC has greater water solubility, we expect to observe enzyme and substrate specific effects of FABP. 11-COOH-THC and 11-COOH-THC-glucuronide are biological markers of THC metabolism so understanding this metabolic pathway is important for developing better methods of characterizing THC use in humans.