# DPD deficiency testing before fluorouracil, capecitabine or tegafur, and dosing by the result

Source: https://onco.cc/protocols/dpyd-testing-before-fluoropyrimidines/  
OnCo record `dpyd-testing-before-fluoropyrimidines` (Protocol). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Before your first dose of fluorouracil (5-FU) given into a vein, capecitabine tablets or tegafur, you should have a blood test for DPD deficiency. A few people break these drugs down very slowly, and a normal dose can make them seriously ill. If the test finds this, the dose is lowered or a different drug is chosen. A normal result does not rule out side effects, so still report them quickly.

## Summary

Fluoropyrimidines are cleared by dihydropyrimidine dehydrogenase (DPD). The EU review of 2020 recommends phenotype and/or genotype testing before systemic fluorouracil, capecitabine or tegafur, contraindicates them in known complete deficiency and advises a reduced starting dose in partial deficiency; the MHRA adopted the same advice for the UK in October 2020 ('test all patients'). Since October 2025 the US capecitabine label also tells prescribers to test for DPYD variants before starting unless treatment is urgent, while noting no FDA-authorised test exists.

There are two ways to test. Genotyping reads the four DPYD variants named in the EU product information (c.1905+1G>A, c.1679T>G, c.2846A>T, c.1236G>A/HapB3), which are considered virtually absent in people of African or Asian ancestry. Phenotyping measures plasma uracil: the EU product information treats 16 to under 150 ng/mL as indicative of partial and 150 ng/mL or more as indicative of complete deficiency, to be read with caution when kidney function is impaired.

Dosing by genotype uses an activity score. CPIC (2017 update) recommends a 50% reduction at activity score 1 (strong) and 25 to 50% at 1.5 (moderate), avoiding fluorouracil and its prodrugs at 0 or 0.5, with the dose raised in later cycles if the first two are tolerated. DPWG (2020) recommends 50% at both 1 and 1.5 and avoiding tegafur below 2, and calls testing 'essential'. Every source says severe toxicity can still occur with a normal result, most often in the first cycle or after a dose increase.

## Fields

- Kind: Protocol
- Last checked: 2026-11-11
- Also known as: DPYD test; DPD test; DPYD genotyping before chemotherapy; uracil test before capecitabine; DPD deficiency screening; fluoropyrimidine pharmacogenetic testing; DPYD activity score dosing

## Connected records

- technologies: [DPYD genotyping and DPD phenotyping before fluoropyrimidines](https://onco.cc/technologies/dpyd-genotyping/), [Fluorouracil dosing by measured blood level](https://onco.cc/technologies/fluorouracil-pharmacokinetic-dosing/), [Pharmacogenomic testing before chemotherapy](https://onco.cc/technologies/oncology-pharmacogenomics/)
- targets: [DPYD](https://onco.cc/targets/dpyd/)
- drugs: [Capecitabine](https://onco.cc/drugs/capecitabine/), [Fluorouracil (5-FU)](https://onco.cc/drugs/fluorouracil/), [Tegafur, gimeracil and oteracil (S-1)](https://onco.cc/drugs/tegafur-gimeracil-oteracil/), [Uridine triacetate](https://onco.cc/drugs/uridine-triacetate/)
- terms: [Dose reduction, interruption and discontinuation](https://onco.cc/terms/dose-modification/), [Living with FOLFIRINOX, NALIRIFOX and gemcitabine with nab-paclitaxel](https://onco.cc/terms/chemotherapy-side-effects-pancreatic/), [Living with FOLFOX, CAPOX, FOLFIRI and the EGFR antibodies](https://onco.cc/terms/chemotherapy-side-effects-colorectal/), [Mucositis and stomatitis](https://onco.cc/terms/mucositis/), [Neutropenia](https://onco.cc/terms/neutropenia/), [Pharmacogenomics](https://onco.cc/terms/pharmacogenomics-term/)
- key papers: [DPYD genotype-guided dose individualisation of fluoropyrimidine therapy in patients with cancer: a prospective safety analysis](https://onco.cc/key-papers/paper-henricks-lancet-oncol/)
- ideas: [Test DPYD, UGT1A1 and TPMT/NUDT15 before the first dose, everywhere](https://onco.cc/ideas/idea-tr1-pre-emptive-pharmacogenomic-testing/)
- protocols: [Anticancer treatment prescribing and pharmacy verification before each cycle](https://onco.cc/protocols/sact-prescribing-and-pharmacy-verification/), [Oral anticancer medicines at home: prescribing, teaching, adherence, storage, handling and disposal](https://onco.cc/protocols/oral-anticancer-medicines-at-home/)

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