What you carry at this position in your DNA and what research says about it.
Medication Response: 8/10 evidence, 9 publications.
You're viewing every possible genotype for this variant.
None of these is your result. Use the genotype toggle to compare them, then sign up and upload your DNA to see which one is yours.
Sample genotype (not yours): G/G
Typical Medication Response and Baseline Lipoprotein Levels
Standard transporter activity ensures normal processing and clearance of several common medications. Typical therapeutic responses are expected when taking drugs like morphine or sumatriptan.
What this genotype means: Standard clearance of morphine and sumatriptan; Typical sensitivity to tramadol; Baseline lipoprotein(a) levels.
Sample genotype (not yours): A/A
Significantly Altered Medication Response and Lower Lipoprotein Levels
Two copies of the variant allele severely limit transporter activity, leading to prolonged drug exposure and altered medication efficacy. Close attention to drug dosing and potential side effects may be beneficial.
What this genotype means: Significantly slower clearance of morphine and sumatriptan; Increased risk of side effects from fenoterol; Lower lipoprotein(a) levels.
Sample genotype (not yours): G/A
Altered Medication Response and Lower Lipoprotein Levels
A single copy of the variant allele reduces transporter activity, which can slow the clearance of certain medications. This may increase sensitivity to some pain relievers while reducing the efficacy of others.
What this genotype means: Slower clearance of morphine and sumatriptan; Potentially greater sensitivity to tramadol; Slightly lower lipoprotein(a) levels.
Gene function and biological role
Gene Function: The SLC22A1 gene encodes the organic cation transporter 1 (OCT1), a protein primarily located in the liver. This transporter plays a critical role in moving various organic compounds and medications from the bloodstream into liver cells. By facilitating this cellular entry, OCT1 directly influences how the body processes, utilizes, and clears these substances. Variations in this gene can significantly alter transporter activity, leading to differences in drug efficacy and the risk of side effects.
Variant Impact: The rs34130495 variant, also known as Gly401Ser, represents a missense mutation in the SLC22A1 gene. This genetic change replaces the amino acid glycine with serine at position 401 of the transporter protein, resulting in a reduced-activity transporter. Because of this structural alteration, the transport of several medications into liver cells is significantly impaired. Consequently, individuals carrying this variant may experience altered drug levels in their bloodstream and modified therapeutic responses.
Key Insight: This variant acts like a cellular gatekeeper that has gone on strike, slowing down the liver's ability to absorb and clear several common pain relievers and diabetes medications.
Location: SLC22A1. Chromosome 6 · 6q25.3 · 160.1 Mb
Estimated prevalence by population
Global 96.8%; European 94.6%; African 99.1%; East Asian 100.0%; South Asian 99.6%; Americas 98.3%; Ashkenazi 98.0%; Finnish 96.6%; Middle Eastern 99.3%; Amish 92.2%.
Estimated GG genotype frequency.
Global 3.2%; European 5.3%; African 0.9%; East Asian 0.0%; South Asian 0.4%; Americas 1.7%; Ashkenazi 2.0%; Finnish 3.4%; Middle Eastern 0.7%; Amish 7.6%.
Estimated GA genotype frequency.
Global < 0.1%; European 0.1%; African < 0.1%; East Asian 0.0%; South Asian < 0.1%; Americas < 0.1%; Ashkenazi < 0.1%; Finnish < 0.1%; Middle Eastern < 0.1%; Amish 0.2%.
Estimated AA genotype frequency.
Showing effects for G/G genotype
Pharmacogenomics
Pain Medication Response
Morphine Metabolism. Evidence: 6/10. Source: PMID 23859569. Typical.
Tramadol Response. Evidence: 5/10. Source: PMID 27541716. Typical.
Organ Systems
Respiratory Health
Fenoterol Sensitivity. Evidence: 5/10. Source: PMID 28791698. Typical Risk.
Neurology & Mental Health
Headache & Migraine
Sumatriptan Response. Evidence: 5/10. Source: PMID 26659468. Typical.
Cardiovascular & Metabolic
Lipids & Cholesterol
Lipoprotein(a) Levels. Evidence: 8/10. Source: PMID 33462484. Typical.
Showing effects for A/A genotype
Morphine Metabolism. Evidence: 6/10. Source: PMID 23859569. Slower Metabolism.
Tramadol Response. Evidence: 5/10. Source: PMID 27541716. Higher Sensitivity.
Fenoterol Sensitivity. Evidence: 5/10. Source: PMID 28791698. Higher Risk.
Sumatriptan Response. Evidence: 5/10. Source: PMID 26659468. Slower Metabolism.
Lipoprotein(a) Levels. Evidence: 8/10. Source: PMID 33462484. Lower.
Showing effects for G/A genotype
Lipoprotein(a) Levels. Evidence: 8/10. Source: PMID 33462484. Slightly Lower.
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Having two copies of the common G allele results in fully functional organic cation transporter 1 (OCT1) proteins. This standard transporter activity allows for normal uptake of medications into liver cells, where they can be metabolized or exert their therapeutic effects. Standard clearance rates are maintained for pain medications like morphine and tramadol, as well as migraine treatments like sumatriptan [1] [2] [3]. While drug processing is optimal, this genotype is also associated with typical baseline levels of lipoprotein(a), a cardiovascular biomarker [4]. Overall, standard clinical guidelines and dosing strategies apply to this genetic profile.
Standard clearance of morphine and sumatriptan; Typical sensitivity to tramadol; Baseline lipoprotein(a) levels.
Sample genotype: AA (Homozygous)
Possessing two copies of the variant A allele results in a highly compromised organic cation transporter 1 (OCT1) protein. This severe loss of transporter function significantly hinders the liver's capacity to clear and metabolize several widely used medications. Research indicates that this profile leads to substantially slower clearance of morphine, which can elevate systemic drug levels and increase the risk of adverse reactions [1]. Similarly, the cardiovascular side effects of medications like fenoterol may be more pronounced due to increased systemic exposure [2]. While the efficacy of some drugs may be reduced due to poor hepatic uptake, patients are often more sensitive to tramadol for postoperative pain relief [3]. Additionally, this genotype is associated with lower levels of lipoprotein(a), a known risk factor for heart disease [4].
Significantly slower clearance of morphine and sumatriptan; Increased risk of side effects from fenoterol; Lower lipoprotein(a) levels.
Sample genotype: GA (Heterozygous)
Carrying one copy of the serine-encoding A allele leads to a partially functional organic cation transporter 1 (OCT1) protein. This reduction in transporter activity impairs the liver's ability to take up and process specific drugs from the bloodstream. Clinical studies show that individuals with this profile exhibit slower metabolism of morphine, potentially increasing drug exposure and the risk of side effects [1]. Conversely, postoperative tramadol consumption may be reduced because of altered drug dynamics [2]. The uptake of sumatriptan is also slowed, which can affect how the body processes this migraine medication [3]. On the beneficial side, this genetic variation is linked to lower circulating levels of lipoprotein(a), which may offer mild cardiovascular advantages [4].
Slower clearance of morphine and sumatriptan; Potentially greater sensitivity to tramadol; Slightly lower lipoprotein(a) levels.
Variants with shared genetic architecture
rs12208357 · SLC22A1 Gene · Chr 6 · Cholesterol and Drug Response
rs1564348 · SLC22A1 Gene · Chr 6 · Cholesterol Levels
rs2297374 · SLC22A1 Gene · Chr 6 · Cholesterol Levels
OCT1 genetic variants influence the pharmacokinetics of morphine in children.
Genetics of 35 blood and urine biomarkers in the UK Biobank.
Content updated August 2026.
ReadYourDNA provides educational interpretation of DNA data you already have. It is not diagnostic, not a substitute for professional medical advice, diagnosis, or treatment, and is not intended to diagnose, treat, cure, or prevent any disease. Talk to a clinician before acting on any result.
Raw DNA Data Reports for 23andMe & AncestryDNA · About ReadYourDNA · FAQ · Methodology & Science · Pricing · Support and complaints · Legal & Contact · Health Traits · Pharmacogenomics · Carrier Status · Variant Explorer · The Human Karyotype · Privacy Policy · Terms of Service · Accessibility · Consumer Health Data Privacy · Your Privacy Choices · Editorial Standards · Your Data, Checkable · Sample Report · ReadYourDNA and Promethease compared · What is inside a 23andMe raw data file · What is inside an AncestryDNA raw data file · What a chatbot can and cannot do with your raw DNA file · Where a raw DNA file can still be uploaded in 2026
Written, maintained and operated by Martin Pechhacker, sole proprietor, Vienna, Austria. Trade register GISA 40064420. support@readyourdna.com