Colorectal cancer (CRC) is the second leading cause of cancer deaths worldwide. One key reason is the lack of durable therapies that target KRAS-dependent disease, which represents approximately 40% of CRC cases. Here, we use liquid chromatography/mass spectrometry (LC/MS) analyses on Drosophila CRC tumour models to identify multiple metabolites in the glucuronidation pathway-a toxin clearance pathway that impacts most drugs-as upregulated in trametinib-resistant RAS/APC/P53 ("RAP") tumours compared to trametinib-sensitive Ras(G12V) single mutant tumours. Genetic inhibition of different steps along the glucuronidation pathway strongly reversed RAP resistance to trametinib; conversely, elevating glucuronidation pathway activity was sufficient to direct trametinib resistance in Ras(G12V) animals. Mechanistically, pairing oncogenic RAS with hyperactive WNT activity strongly elevated PI3K/AKT/GLUT signalling, which in turn directed elevated glucose uptake and glucuronidation; our data also implicate the pentose phosphate pathway in this process. We provide evidence that this mechanism of trametinib resistance is conserved in a KRAS/APC/TP53 mouse CRC tumour organoid model. Finally, we identify two clinically accessible approaches to inhibiting drug glucuronidation: (i) blocking an initial HDAC1-mediated deacetylation step of trametinib with the FDA-approved drug vorinostat; (ii) reducing blood glucose by the alpha-glucosidase inhibitor acarbose. Overall, our observations demonstrate a key mechanism by which oncogenic RAS/WNT activity promotes increased drug clearance in CRC and provides a practical path towards abrogating drug resistance in CRC tumours.