UDP Glucuronosyltransferase Family 1 Member A1
UGT1A1 clears bilirubin (the molecule that builds up in jaundice) and several drugs including irinotecan and nilotinib.[1] A variant called *28, common in people of all ancestries, reduces UGT1A1 activity. It's the cause of Gilbert's syndrome, a benign condition, but it also makes cancer patients much more susceptible to severe side effects from irinotecan-based chemotherapy.[2]
Gene2Rx reports your UGT1A1 genotype across 8 named star alleles, built from 7 variants curated by PharmVar.
Star alleles (like *1, *2, *4) are standardized names for distinct versions of a pharmacogene. *1 is the reference; higher numbers identify variants discovered later that change the enzyme's activity.
You inherit one allele from each parent, so your genotype is a pair (e.g. *1/*4). The pair determines your predicted phenotype — for example, whether you metabolize a drug at a normal, decreased, or no-function rate.
PharmVar is the international registry that defines and curates these allele names. Gene2Rx tests the variants required to call every UGT1A1 allele in the PharmVar catalog.
Gene2Rx covers 6 medications with published pharmacogenetic guidance for UGT1A1, drawn from CPIC and FDA sources. Each drug links to its full pharmacogenetics page.
These branded medications include at least one active ingredient whose metabolism or action involves UGT1A1. Each links to its full pharmacogenetic breakdown.
This page lists drugs affected by UGT1A1. A Gene2Rx report tells you which metabolizer group you fall into, and what that means for every medication on this list.
Get your report Look up a medicationInformational only, not medical advice. The presence of a UGT1A1 pharmacogenetic guideline does not mean every patient needs to change their dose. Never start, stop, or change a medication without talking to your prescribing clinician.