According to a commentary, despite the amount of clinical evidence on the deleterious effect of dihydropyrimidine dehydrogenase (DPD) deficiency in fluorouracil-treated patients, and fluorouracil being the most widely prescribed anticancer drug worldwide, DPD testing is still not officially recommended by health agencies and is far from being standard practice in the clinic. The commentator notes that though recent studies have been done in large cohorts, most of the clinical studies of the relation between DPD status and clinical outcome have been done at single centres, often retrospectively, thus failing to meet the level of evidence health agencies require for drug safety labelling changes. In addition, the issue of deciding the best strategy for detection of DPD-deficiency in patients, with acceptable sensitivity and specificity, remains far from being elucidated. In meantime, there are initiatives undertaken to issue recommendations, such as those by the Clinical Pharmacogenetics Implementation Consortium, which aim to help clinicians to secure the administration of fluorouracil by upfront screening of potential DPD deficiency. These guidelines are expected to be regularly updated with the latest clinical evidence.