What you carry at this position in your DNA and what research says about it.
Drug Response and Cancer Risk: 6/10 evidence, 12 publications.
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Sample genotype (not yours): T/T
Lower Risk of Bleeding and Lung Cancer
Two copies of the common T allele are associated with typical drug transport efficiency. This genotype is linked to a lower risk of lung cancer and typical bleeding risk on direct oral anticoagulants compared to carriers of the C variant.
What this genotype means: Typical bleeding risk on blood thinners; Lower susceptibility to lung cancer; Slightly higher risk of gallstones.
Sample genotype (not yours): C/C
Higher Bleeding and Lung Cancer Risk
Two copies of the C allele significantly increase the risk of bleeding when taking direct oral anticoagulants. This genotype is also linked to higher lung cancer susceptibility and slower metabolism of several medications.
What this genotype means: Increased bleeding risk on direct oral anticoagulants; Higher susceptibility to lung cancer; Slower metabolism of efavirenz and rifampin.
Sample genotype (not yours): T/C
Increased Risk of Lung Cancer
Carrying one copy of the C allele is associated with a higher susceptibility to lung cancer, particularly in women. It also leads to slower metabolism of certain medications like tenofovir alafenamide.
What this genotype means: Higher susceptibility to lung cancer; Slower metabolism of tenofovir alafenamide; Typical bleeding risk on blood thinners.
Gene function and biological role
Gene Function: The ABCB1 gene encodes P-glycoprotein, a crucial ATP-dependent drug efflux pump expressed in protective tissue barriers [1]. This transporter is highly active in the intestines, liver, kidneys, and blood-brain barrier, where it pumps foreign substances and medications out of cells [1]. By limiting the absorption and facilitating the elimination of various compounds, ABCB1 plays a major role in determining drug exposure and efficacy [2]. It also helps protect tissues from environmental toxins and carcinogens [3]. Variations in this gene can significantly alter transporter expression and activity, leading to wide differences in drug response and disease susceptibility [1] [2].
Variant Impact: The rs3842 variant is located in the 3 prime untranslated region of the ABCB1 gene, a region critical for regulating mRNA stability and translation [1]. The C allele alters the regulatory binding sites, which can lead to changes in P-glycoprotein expression levels [1]. This molecular change affects the transport of various therapeutic drugs, including anticoagulants and antivirals [4] [5]. It also influences the cellular export of inhaled carcinogens, potentially modifying susceptibility to lung cancer [3].
Key Insight: The same genetic variant that alters how your body processes common blood thinners also influences your susceptibility to lung cancer from inhaled toxins.
Location: ABCB1. Chromosome 7 · 7q21.12 · 87.5 Mb
Estimated prevalence by population
Global 71.1%; European 73.7%; African 68.0%; East Asian 52.5%; South Asian 68.9%; Americas 74.5%; Ashkenazi 65.3%; Finnish 72.4%; Middle Eastern 76.3%; Amish 76.3%.
Estimated TT genotype frequency.
Global 26.4%; European 24.3%; African 28.9%; East Asian 39.9%; South Asian 28.2%; Americas 23.6%; Ashkenazi 31.0%; Finnish 25.4%; Middle Eastern 22.1%; Amish 22.1%.
Estimated TC genotype frequency.
Global 2.6%; European 2.0%; African 3.1%; East Asian 7.6%; South Asian 2.9%; Americas 1.9%; Ashkenazi 3.7%; Finnish 2.2%; Middle Eastern 1.6%; Amish 1.6%.
Estimated CC genotype frequency.
Showing effects for T/T genotype
Pharmacogenomics
Anticoagulant & Blood Thinner Response
Bleeding Risk on Medication. Evidence: 6/10. Source: PMID 36145636. Typical Risk.
Antimicrobial & Antiviral Response
Efavirenz Metabolism. Evidence: 5/10. Source: PMID 19916993. Typical.
Rifampin Metabolism. Evidence: 5/10. Source: PMID 38315168. Typical.
Tenofovir Levels. Evidence: 5/10. Source: PMID 39426598. Typical.
Antidepressant & Psychiatric Drug Response
Olanzapine Response. Evidence: 5/10. Source: PMID 33378980. Typical.
Cancer & Oncology
Lung Cancer
Lung Cancer. Evidence: 3/10. Source: PMID 19107762. Typical Risk.
Organ Systems
Digestive & Gut Disorders
Gallstones. Evidence: 6/10. Source: PMID 39789286. Increased Risk.
Showing effects for C/C genotype
Bleeding Risk on Medication. Evidence: 6/10. Source: PMID 36145636. Increased Risk.
Efavirenz Metabolism. Evidence: 5/10. Source: PMID 19916993. Slower Metabolism.
Rifampin Metabolism. Evidence: 5/10. Source: PMID 38315168. Slower Metabolism.
Olanzapine Response. Evidence: 5/10. Source: PMID 33378980. Heart Rhythm Risk.
Lung Cancer. Evidence: 3/10. Source: PMID 19107762. Increased Risk.
Gallstones. Evidence: 6/10. Source: PMID 39789286. Typical Risk.
Showing effects for T/C genotype
Tenofovir Levels. Evidence: 5/10. Source: PMID 39426598. Slower Metabolism.
What this genotype means for the people who carry it
Sample genotype: TT (Homozygous)
Typical P-glycoprotein expression is maintained by this genotype, ensuring standard drug transport and toxin clearance [1]. Individuals with this genotype have a typical risk of bleeding when treated with direct oral anticoagulants like edoxaban or apixaban [2]. They also exhibit standard clearance rates for antiretroviral therapies such as efavirenz [3]. Furthermore, this genotype is associated with a lower susceptibility to lung cancer compared to carriers of the C allele [4]. However, some genetic studies suggest a slightly increased risk of developing gallstones [5]. Overall, this genotype represents the baseline for most drug transport pathways.
Typical bleeding risk on blood thinners; Lower susceptibility to lung cancer; Slightly higher risk of gallstones.
Sample genotype: CC (Homozygous)
Two copies of the C allele significantly alter the expression of the P-glycoprotein transporter [1]. This genotype is strongly linked to an increased risk of bleeding complications when taking direct oral anticoagulants such as edoxaban, apixaban, and rivaroxaban [2]. It also leads to slower metabolism and higher exposure levels of the antiretroviral drug efavirenz [3] and the antibiotic rifampin [4]. Furthermore, individuals with this genotype have an increased susceptibility to lung cancer, especially women [5]. When treated with the antipsychotic olanzapine, they may also face an increased likelihood of heart rhythm disorders [6].
Increased bleeding risk on direct oral anticoagulants; Higher susceptibility to lung cancer; Slower metabolism of efavirenz and rifampin.
Sample genotype: TC (Heterozygous)
Carrying one copy of the C allele alters the regulation of ABCB1, leading to modified P-glycoprotein expression [1]. This genotype is associated with an increased susceptibility to lung cancer, particularly in women, due to potentially reduced export of inhaled carcinogens [2]. In terms of medication response, individuals with this genotype may experience slower metabolism and higher plasma concentrations of tenofovir alafenamide [3]. However, they maintain typical bleeding risks on direct oral anticoagulants compared to those with the C/C genotype [4]. They also exhibit faster metabolism of the antipsychotic medication olanzapine [5].
Higher susceptibility to lung cancer; Slower metabolism of tenofovir alafenamide; Typical bleeding risk on blood thinners.
Variants with shared genetic architecture
rs1045642 · ABCB1 Gene · Chr 7 · Medication Response
rs2032582 · ABCB1 Gene · Chr 7 · Lung Cancer Risk
rs1128503 · ABCB1 Gene · Chr 7 · Medication Response
Association between Genetic Polymorphisms and Bleeding in Patients on Direct Oral Anticoagulants.
A scalable variational inference approach for increased mixed-model association power.
Content updated August 2026.
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