The FDA updated Genentech’s Xeloda (capecitabine) label to include explicit language recommending testing for DPYD variants before initiating therapy, and added a boxed warning noting that complete DPD deficiency can cause severe adverse reactions or death. The agency moved from a prior 'consider testing' stance to a clearer test‑first recommendation when clinical circumstances permit. DPYD encodes dihydropyrimidine dehydrogenase (DPD), the primary enzyme for fluoropyrimidine metabolism; deficient patients can accumulate toxic drug levels leading to severe mucositis, neutropenia, neurotoxicity and fatal outcomes. The label change reflects input from patient advocates, oncologists and recent evidence supporting clinical utility of preemptive genotyping. The revision will drive broader adoption of pharmacogenetic screening in oncology practice, influence guideline panels and payer coverage decisions, and prompt labs and clinics to operationalize rapid DPYD testing prior to fluoropyrimidine administration.