Identifying polymorphisms in the dihydropyrimidine dehydrogenase (DPYD) genes is gaining importance as predictors of fluoropyrimidine-associated toxicity. The recommendation of dose adjustment for chemotherapy guided by the presence of polymorphisms of the DPYD gene can potentially improve treatment safety for a large number of patients, saving lives, avoiding complications and reducing health care costs. This article discusses how personalisation of fluoropyrimidine treatment based on the identification of DPYD variants can mitigate toxicities and be cost effective.