The U.S. Food and Drug Administration (FDA) is providing this communication to increase awareness of recent updates to the product labeling of capecitabine (Xeloda) and fluorouracil (5-FU) related to risks associated with dihydropyrimidine dehydrogenase (DPD) deficiency. All healthcare providers should be aware of the risks of DPD deficiency, inform patients prior to treatment about the potential for serious and life-threatening toxicities due to DPD deficiency, and test patients for genetic variants of DPYD prior to initiating treatment with capecitabine or 5-FU unless immediate treatment is necessary.