CYP2C19 rs12765683: Understanding Pharmacogenomic Variability
The rs12765683 variant is located within the CYP2C19 gene, which encodes an enzyme responsible for metabolizing various medications. Research investigates how this and other variants in the locus may influence the body's processing of drugs like clopidogrel and certain proton-pump inhibitors.
What each genotype means
Typical baseline CYP2C19 metabolism
Research indicates that the homozygous reference CC genotype at rs12765683 reflects baseline genomic sequence at this position within the CYP2C19 locus. Because this variant is primarily cataloged as being in linkage disequilibrium with functional CYP2C19 star alleles rather than directly causing altered activity itself, evidence for an independent clinical effect is limited. If you are taking medications metabolized by CYP2C19 such as clopidogrel or proton pump inhibitors, consult your doctor or pharmacist to interpret your comprehensive CYP2C19 star-allele panel before considering any dosing changes.
Carried by approximately 45% to 70% of individuals across global populations, representing the most common genotype at this locus.
Heterozygous tag variant carrier
Carrying one copy of the T allele at rs12765683 statistically tags haplotypes linked to altered CYP2C19 drug metabolism in population pharmacogenomic studies. Direct clinical evidence for rs12765683 alone remains limited, meaning true metabolic activity depends on which specific functional star alleles are present on your CYP2C19 gene copies. If you are prescribed drugs such as clopidogrel or acid-reducing proton pump inhibitors, discuss standard multi-variant pharmacogenomic testing and personalized dosing with your clinician or pharmacist.
Found in approximately 25% to 45% of individuals worldwide, reflecting common carriage across European, African, and Asian ancestries.
Homozygous tag variant carrier
Carrying two copies of the alternate T allele at rs12765683 indicates homozygous status for this linked tag variant within the CYP2C19 gene cluster. While pharmacogenomic studies evaluate this locus in association with variable clopidogrel and proton pump inhibitor efficacy, evidence regarding direct functional consequences of this single nucleotide change is limited and requires haplotype context. Do not alter any medication regimen independently; speak with your physician or pharmacist regarding comprehensive CYP2C19 genotyping to assess your precise metabolic profile.
Observed in roughly 2% to 12% of individuals globally, corresponding to the observed minor allele frequency range of 0.15 to 0.35.
What is the rs12765683 Variant?
The rs12765683 variant is a specific genetic change located within the CYP2C19 gene. In genomics, a single nucleotide polymorphism (SNP) like rs12765683 represents a variation at a single position in the DNA sequence. This gene is situated on chromosome 10 and provides instructions for creating an enzyme that plays a critical role in the liver. This enzyme is part of the cytochrome P450 family, a group of proteins essential for breaking down, or metabolizing, a wide array of substances, including many prescription medications. Because this variant sits within a region involved in drug metabolism, researchers study it to understand why individuals may process the same medication at different rates. It is important to note that rs12765683 is one of many variations within this gene, and its presence is often analyzed alongside other known alleles to determine an individual's overall metabolic profile.
The Role of the CYP2C19 Gene
The CYP2C19 gene is a cornerstone of pharmacogenomics, the study of how genes affect a person's response to drugs. The enzyme produced by this gene is responsible for the metabolism of several clinically important medications. For example, it helps convert the antiplatelet drug clopidogrel from its inactive form into its active, therapeutic form. It also breaks down proton-pump inhibitors (PPIs), which are used to treat acid reflux, and certain antifungal medications like voriconazole. Variations in this gene can lead to different enzyme activity levels, often categorized as poor, intermediate, normal, or ultra-rapid metabolizers. When an individual carries variants that reduce the enzyme's function, they may not activate certain drugs effectively or may clear others too slowly. Conversely, increased function can lead to faster drug clearance. Understanding these genetic differences helps clinicians consider whether a standard dose is appropriate or if an alternative therapy might be more effective for a specific patient.
Research and Evidence Strength
The evidence linking specific CYP2C19 variants to clinical outcomes is robust for some alleles, such as *2 and *3, but remains limited or evolving for others like rs12765683. While large-scale studies have established that reduced-function alleles are associated with lower clopidogrel efficacy and increased risk of adverse cardiovascular events in certain populations, the specific impact of every individual SNP in the locus is not always fully characterized. Research often shows mixed results, with some studies finding significant associations between genotype and drug response, while others report less clear outcomes. This heterogeneity can be due to differences in study design, the specific medications tested, and the ancestral backgrounds of the participants. Because the field of pharmacogenomics is rapidly advancing, guidelines from organizations like the Clinical Pharmacogenetics Implementation Consortium (CPIC) are frequently updated to reflect the latest evidence. Readers should view genetic information as one piece of a larger clinical puzzle and always consult with a healthcare provider to interpret how these findings apply to their specific health situation.
Navigating Your Genetic Information
If you have received information about your CYP2C19 genotype, it is natural to have questions about what it means for your health. It is essential to understand that a genetic variant is not a medical diagnosis. Many factors beyond genetics—such as age, diet, liver function, and other medications you may be taking—influence how your body responds to drugs. You cannot and should not use this information to change your medication dosage or stop taking a prescribed treatment on your own. Doing so could be dangerous. Instead, use this information as a starting point for a conversation with your doctor or pharmacist. They can evaluate your genetic results in the context of your full medical history and current treatment plan. If your clinician determines that your genotype is relevant to your care, they may suggest adjusting your medication or choosing an alternative therapy that is better suited to your metabolic profile.
How common is this variant?
The rs12765683 variant is common across multiple continental ancestries, with a minor allele frequency typically ranging between 0.15 and 0.35.
Frequently asked questions
Does having a CYP2C19 variant mean I am allergic to my medication?
No, a genetic variant in CYP2C19 is not an allergy. It simply means your body may process or metabolize a medication differently than the average person, which can affect how well the drug works or how long it stays in your system.
Should I get tested for CYP2C19 variants before starting a new drug?
Routine genetic testing is not required for everyone. Your doctor will decide if testing is necessary based on the specific medication being prescribed and your individual clinical needs.
Can I change my medication dose based on my genotype?
Never change your medication dose on your own. Any adjustments to your treatment must be made by your healthcare provider, who will consider your genetic results alongside other important health factors.
Are all CYP2C19 variants the same?
No, there are many different variants within the CYP2C19 gene, and they can have very different effects on enzyme function. Some variants may significantly reduce function, while others may have little to no impact.
Sources & further reading
Educational information only, last refreshed 10/28/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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The CYP2C19*2 loss-of-function splicing defect results in impaired biotransformation of prodrugs including clopidogrel and altered clearance of proton pump inhibitors and select antidepressants.
Defines the CYP2C19*17 increased function allele, conferring rapid or ultrarapid metabolism for CPIC-actionable drugs including clopidogrel, PPIs, and SSRIs.
Defines the CYP2C19*8 loss-of-function variant (c.358T>C, p.Trp120Arg) which results in no enzymatic activity and impaired metabolism of CYP2C19 substrates.
Defines the non-functional CYP2C19*3 null allele resulting from a premature stop codon, leading to poor metabolism of drugs such as clopidogrel, escitalopram, and proton pump inhibitors.
Defines the CYP2C19*4 allele caused by an ATG start codon alteration that abolishes translation, resulting in reduced or absent drug metabolism capacity.
Known as CYP2C19*3, this premature stop codon (c.636G>A, p.Trp212Ter) results in a complete loss-of-function phenotype for clopidogrel and antidepressant metabolism.