What you carry at this position in your DNA and what research says about it.
Chemotherapy Toxicity: 6/10 evidence, 20 publications.
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Sample genotype (not yours): A/A
Typical Chemotherapy Toxicity Risk
Standard dihydropyrimidine dehydrogenase enzyme activity supports normal clearance of fluoropyrimidine chemotherapy drugs. This genotype is associated with a lower risk of severe side effects during standard treatments.
What this genotype means: Normal chemotherapy clearance; Lower risk of severe drug toxicity.
Sample genotype (not yours): A/G
Increased Chemotherapy Toxicity Risk
Presence of a single G variant allele is associated with a higher risk of severe side effects from certain chemotherapy drugs. These side effects can include severe diarrhea, hand-foot syndrome, and nerve damage.
What this genotype means: Elevated risk of chemotherapy side effects; Potential for slower drug clearance.
Sample genotype (not yours): G/G
Higher Chemotherapy Toxicity Risk
Possessing two copies of the G variant is linked to slower metabolism of fluoropyrimidine chemotherapy drugs. This can significantly increase the risk of severe toxicities, including hand-foot syndrome and infections.
What this genotype means: Slower chemotherapy metabolism; Significantly higher risk of drug toxicity.
Gene function and biological role
Gene Function: The DPYD gene encodes dihydropyrimidine dehydrogenase, an enzyme responsible for breaking down pyrimidines in the body [1]. This enzyme performs the rate-limiting step in clearing fluoropyrimidine chemotherapy drugs like 5-fluorouracil and capecitabine [1]. When dihydropyrimidine dehydrogenase activity is reduced, these chemotherapy medications can accumulate to toxic levels [2]. This accumulation can lead to severe, potentially life-threatening side effects during cancer treatment [2].
Variant Impact: Known also as DPYD*9A or C29R, this genetic change alters the amino acid cysteine to arginine at position 29 of the dihydropyrimidine dehydrogenase enzyme [3]. This specific alteration has been widely studied for its impact on enzyme activity and drug clearance [4]. While some clinical guidelines classify it as having normal function, several studies suggest it may alter sensitivity to chemotherapy [4]. The G allele is relatively common across many populations, particularly in those of African and European ancestry.
Key Insight: Although some clinical databases classify this variant as normal, multiple clinical trials have linked it to a higher rate of severe chemotherapy side effects like hand-foot syndrome and neuropathy.
Location: DPYD. Chromosome 1 · 1p21.3 · 97.9 Mb
Estimated prevalence by population
Global 53.6%; European 60.0%; African 35.5%; East Asian 86.1%; South Asian 56.7%; Americas 56.6%; Ashkenazi 79.1%; Finnish 51.5%; Middle Eastern 60.7%; Amish 60.8%.
Estimated AA genotype frequency.
Global 38.2%; European 34.9%; African 48.2%; East Asian 13.3%; South Asian 37.2%; Americas 37.3%; Ashkenazi 19.7%; Finnish 40.5%; Middle Eastern 34.4%; Amish 34.4%.
Estimated AG genotype frequency.
Global 8.3%; European 5.1%; African 16.3%; East Asian 0.5%; South Asian 6.1%; Americas 6.1%; Ashkenazi 1.2%; Finnish 8.0%; Middle Eastern 4.9%; Amish 4.9%.
Estimated GG genotype frequency.
Showing effects for A/A genotype
Pharmacogenomics
Chemotherapy Response
Chemotherapy Toxicity. Evidence: 6/10. Source: PMID 30114658. Lower Risk.
Cardiovascular & Metabolic
Obesity & Body Composition
Body Mass Index. Evidence: 8/10. Source: PMID 29273807. Typical BMI.
Showing effects for A/G genotype
Chemotherapy Toxicity. Evidence: 6/10. Source: PMID 30114658. Increased Risk.
Body Mass Index. Evidence: 8/10. Source: PMID 29273807. Slightly Higher BMI.
Showing effects for G/G genotype
Chemotherapy Toxicity. Evidence: 6/10. Source: PMID 30114658. Higher Risk.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Standard dihydropyrimidine dehydrogenase enzyme activity supports normal clearance of fluoropyrimidine chemotherapy drugs [1]. This genotype is associated with a lower risk of severe side effects during standard treatments [1]. Clinical studies show that carrying two copies of the standard A allele is linked to a decreased risk of drug toxicity compared to carrying the variant G allele [2]. Patients with this genotype typically experience standard drug metabolism and survival rates when undergoing common chemotherapy regimens like FOLFOX or XELOX [3]. No dosage adjustments are generally recommended based on this variant alone.
Normal chemotherapy clearance; Lower risk of severe drug toxicity.
Sample genotype: AG (Heterozygous)
Presence of a single G variant allele is associated with a higher risk of severe side effects from certain chemotherapy drugs [1]. These side effects can include severe diarrhea, hand-foot syndrome, and nerve damage [2]. Some clinical studies have observed decreased survival rates and increased neuropathy in patients treated with regimens like FOLFOX or XELOX [3]. While some professional guidelines classify this variant as having normal function, other research suggests it may cause partial enzyme impairment under certain conditions [1]. Discussing these genetic findings with an oncology team can help guide personalized treatment monitoring.
Elevated risk of chemotherapy side effects; Potential for slower drug clearance.
Sample genotype: GG (Homozygous)
Possessing two copies of the G variant is linked to slower metabolism of fluoropyrimidine chemotherapy drugs [1]. This can significantly increase the risk of severe toxicities, including hand-foot syndrome and infections [2]. Clinical trials have reported increased rates of gastrointestinal toxicity, neuropathy, and decreased overall survival in patients undergoing standard chemotherapy [3]. Although some major guidelines do not mandate dose reductions for this specific variant, clinical evidence suggests a higher susceptibility to adverse drug reactions [1]. Sharing these results with healthcare providers allows for closer monitoring during cancer therapies.
Slower chemotherapy metabolism; Significantly higher risk of drug toxicity.
Variants with shared genetic architecture
rs56038477 · DPYD Gene · Chr 1 · Chemotherapy Toxicity Risk
rs75017182 · DPYD Gene · Chr 1 · Chemotherapy Drug Toxicity
rs17376848 · DPYD Gene · Chr 1 · Chemotherapy Toxicity Risk
Content updated August 2026.
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