Skip to content
Use your HSA or FSA funds
Sequence your genome (opens in a new tab)

Gene

UGT1A1

UDP glucuronosyltransferase family 1 member A1

Summary

Cytogenetic location
2q37.1
Coordinates
Chromosome 2: 233,760,270–233,773,300 (GRCh38)
Exons
5 exons across 13 kb
Protein
533 amino acids
Inheritance
Autosomal recessive
Also known as
UGT1A
Previous symbols
UGT1, GNT1
MANE Select transcript
ENST00000305208.10NM_000463.3
Locus type
complex locus constituent
  • Very high
  • Confident
  • Low
  • Very low

Curated report relevant to this gene

  • Gilbert Syndrome

    • Autosomal recessive

      An autosomal recessive inherited disorder characterized by unconjugated hyperbilirubinemia, resulting in harmless intermittent jaundice.

      • 1 GenCC submitter rates it definitive or strong
      What knowing changes

      No treatment required for Gilbert syndrome itself; drug dose adjustment for UGT1A1-metabolized medications

    • Crigler-Najjar SyndromeAutosomal recessive

      Caused by variants in UGT1A1 that severely reduce bilirubin processing, causing persistent and sometimes dangerous jaundice from birth (type 1) or milder lifelong jaundice (type 2).

      • 4 GenCC submitters rate it definitive or strong
      What knowing changes

      Knowing allows daily phototherapy or liver transplant in type 1, and phenobarbital treatment in type 2, to prevent bilirubin brain damage.

Inheritance

Autosomal recessive
It takes a changed copy from each parent. With one, you are a carrier and usually unaffected; when both parents are carriers, each child has a one-in-four chance of inheriting two.

UGT1A1 and medicines

  • Irinotecan, atazanavir & bilirubin handling

    Pharmacogenomics

    UGT1A1 glucuronidates bilirubin, the active metabolite of irinotecan, and is inhibited by the HIV drug atazanavir. Reduced activity (the *28 allele, behind Gilbert syndrome, and *6) raises the risk of irinotecan toxicity and of atazanavir-related jaundice.

    • Most relevant if you receive irinotecan (some colorectal/GI regimens).
    • Relevant if you take atazanavir: reduced activity raises the chance of jaundice, a common reason people stop the drug.
    • Also explains mild, harmless jaundice (Gilbert syndrome) that can appear when fasting or unwell.
    • Also noted on the labels of some cancer drugs, including belinostat, nilotinib and pazopanib.

    Alleles the report reads

    • *1Normal function
    • *6Decreased function

    Results CPIC describes

    • Indeterminate
    • Intermediate Metabolizer
    • Normal Metabolizer
    • Poor Metabolizer
    MedicineCPIC levelGuideline
    atazanavirAUGT1A1 and Atazanavir
    irinotecanA
    belinostatB
    Show 4 more medicines
    MedicineCPIC levelGuideline
    dolutegravirB/C
    nilotinibB/C
    pazopanibB/C
    raltegravirB/C

    Calls the *6 coding variant, common in East Asian populations. The *28 TA-repeat behind Gilbert syndrome cannot be read from single-variant data and is listed under deep analysis; rarer alleles are not assessed.

How UGT1A1 is laid out

  • Coding sequence
  • Untranslated region
  • Intron
  • Direction of transcription
  • Known disease-causing sites
Chromosome 2, with a bracket where UGT1A1 sits. UGT1A1 and 17 genes near it on chromosome 2, from 233,266,785 to 234,266,784.Chromosome 22q37.1p25.3p25.2p25.1p24.3p24.2p24.1p23.3p23.2p23.1p22.3p22.2p22.1p21p16.3p16.2p16.1p15p14p13.3p13.2p13.1p12p11.2p11.1q11.1q11.2q12.1q12.2q12.3q13q14.1q14.2q14.3q21.1q21.2q21.3q22.1q22.2q22.3q23.1q23.2q23.3q24.1q24.2q24.3q31.1q31.2q31.3q32.1q32.2q32.3q33.1q33.2q33.3q34q35q36.1q36.2q36.3q37.1q37.2q37.3233.4 Mb233.6 Mb233.8 Mb234 Mb234.2 MbATG16L1: 233,210,051–233,295,674, forward strandATG16L1SAG: 233,307,816–233,347,055, forward strandSAGDGKD: 233,354,475–233,472,104, forward strandDGKDUSP40: 233,475,526–233,566,783, reverse strandUSP40UGT1A8: 233,617,633–233,773,310, forward strandUGT1A10: 233,636,447–233,773,310, forward strandUGT1A9: 233,671,734–233,773,310, forward strandUGT1A7: 233,681,885–233,773,310, forward strandUGT1A6: 233,691,607–233,773,300, forward strandUGT1A5: 233,712,907–233,773,310, forward strandUGT1A5UGT1A4: 233,718,727–233,773,310, forward strandUGT1A4UGT1A3: 233,729,042–233,773,310, forward strandUGT1A3UGT1A1: 233,760,270–233,773,300, forward strandUGT1A1MROH2A: 233,775,679–233,833,423, forward strandHJURP: 233,833,416–233,854,672, reverse strandHJURPMSL3B: 233,864,663–233,868,413, reverse strandMSL3BTRPM8: 233,917,373–234,019,522, forward strandTRPM8SPP2: 234,050,617–234,108,287, forward strandSPP2Diagram of UGT1A1: 5 exons on the forward strand of chromosome 2Exon 1: 24 known disease-causing sitesExon 2: 2 known disease-causing sitesExon 3: 3 known disease-causing sitesExon 4: 7 known disease-causing sitesExon 5: 7 known disease-causing sitesExon 1: 233,760,270–233,761,151, 882 basesExon 2: 233,767,034–233,767,165, 132 basesExon 3: 233,767,849–233,767,936, 88 basesExon 4: 233,768,220–233,768,439, 220 basesExon 5: 233,772,262–233,773,300, 1,039 bases123455′3′

Exons of the gene's MANE Select transcript (release v1.5), from NCBI and EMBL-EBI, on the GRCh38 reference genome.

Chromosome bands from UCSC's GRCh38 ideogram (2022-10-29).

Nearby genes from Ensembl release 116, on GRCh38.

Exons make up 2.4 kb of the gene's 13 kb; 1,602 of those bases code for the protein.

How a genome test reads UGT1A1

48

positions in UGT1A1 where ClinVar classes a change as pathogenic or likely pathogenic

None of them falls in a region short reads find hard.

A whole genome covers all 13 kb of UGT1A1, introns included, not only the 2.4 kb of exons.

Traits linked to UGT1A1

The Human Phenotype Ontology lists these as features of the rare conditions UGT1A1 can cause. Each trait's page lists the other genes linked to it.

External links

Where this comes from

  • HGNC: the gene's symbol, name, other symbols and location.
  • MANE Select v1.5, from NCBI and EMBL-EBI: the transcript, its exons and coding sequence.
  • GenCC and ClinGen, released 2026-10-16: which conditions the gene is linked to, and how strongly.
  • The ACMG secondary findings list, SF v3.2.
  • ClinVar and the GIAB stratifications: known disease-causing sites, and the regions short reads find hard.
  • CPIC and PharmGKB: the alleles, results and medicines.
  • The Human Phenotype Ontology, release 2026-09-01: the traits linked to the gene. Find out more at hpo.jax.org.
  • Data release 2026.10.16-c6eea6bf.

Cite this page

APA

Dante Labs. (n.d.). UGT1A1 gene: UDP glucuronosyltransferase family 1 member A1. Retrieved 17 October 2026, from https://dantelabs.com/genes/ugt1a1

Vancouver

Dante Labs. UGT1A1 gene: UDP glucuronosyltransferase family 1 member A1 [Internet]. [cited 17 October 2026]. Available from: https://dantelabs.com/genes/ugt1a1

One test. A lifetime of answers.

From $449Free shipping · Results in 6–8 weeks

Get my Genome Test