CYP2D6 rs1799972: Understanding Your Pharmacogenetic Profile
The rs1799972 variant is a single nucleotide polymorphism located within the CYP2D6 gene, which encodes a critical enzyme responsible for metabolizing approximately 25% of clinically prescribed medications. This variant is studied in the context of pharmacogenetics to understand how individual genetic differences may influence the rate at which the body processes drugs used for stress-related and other health conditions.
What each genotype means
Typical baseline metabolic activity
You carry two copies of the common C allele at rs1799972, which is traditionally linked to typical baseline CYP2D6 enzyme activity when part of a normal functional haplotype. In pharmacogenomic research, individuals with this genotype show standard rates of processing for medications broken down by CYP2D6. If you take psychotropic medications or other CYP2D6 substrates, discuss dosing and monitoring directly with your prescribing clinician or pharmacist.
Carried by approximately 85% to 90% of individuals of European and East Asian descent, but less frequent in African ancestry populations (roughly 45%).
Intermediate metabolic activity
You carry one copy of the T allele at rs1799972, a defining single nucleotide variant of the reduced-function CYP2D6*17 haplotype common in African populations. Carrying this variant is statistically associated with moderately reduced clearance rates for certain psychotropic and opioid medications, though overall clinical impact is considered limited and variable depending on other genetic factors. Always consult your doctor or pharmacist prior to making any changes to your medication dosing.
Carried by approximately 40% to 45% of individuals of African ancestry, while remaining rare (under 5%) in European and East Asian populations.
Reduced metabolic activity
You carry two copies of the T variant at rs1799972, which typically corresponds to homozygous reduced-function haplotypes like CYP2D6*17/*17. Research suggests this genotype leads to significantly lower CYP2D6 enzymatic clearance, which can cause higher blood levels or altered side-effect profiles for specific psychotropic medications. Because of these metabolic differences, you should review your medication regimen and potential dose adjustments with your clinician or pharmacist.
Found in approximately 10% to 12% of individuals with Sub-Saharan African ancestry, but observed in less than 0.1% of individuals of European or Asian descent.
What is the rs1799972 Variant?
The rs1799972 variant is a specific change in the DNA sequence of the CYP2D6 gene. In genetics, a single nucleotide polymorphism (SNP) like rs1799972 represents a variation at a single position in the genome. The CYP2D6 gene is located on chromosome 22 and is highly polymorphic, meaning it contains many different variations across the human population. Because this gene is responsible for producing the cytochrome P450 2D6 enzyme, changes in its DNA sequence can potentially alter the structure or the amount of enzyme produced by the liver. Researchers track these specific SNPs to categorize individuals into different metabolizer groups, which helps in understanding why people may respond differently to the same dose of a medication. While rs1799972 is one of many markers identified in this region, it is specifically monitored for its potential role in the metabolic clearance of various psychotropic drugs.
The Role of the CYP2D6 Gene
The CYP2D6 gene provides instructions for making an enzyme that is a member of the cytochrome P450 family. These enzymes are primarily found in the liver and are essential for the metabolism of a wide array of substances, including lipids, hormones, and toxins. In clinical medicine, CYP2D6 is particularly famous for its role in processing roughly one-quarter of all commonly prescribed drugs. This includes antidepressants, antipsychotics, opioids, and certain cardiovascular medications. Because the gene is so variable, individuals can have different 'star alleles'—or versions of the gene—that result in enzyme activity ranging from no function to increased function. This variability is the foundation of pharmacogenetics, a field that aims to tailor drug therapy to an individual's genetic makeup. By understanding how a person's CYP2D6 genotype influences their enzyme activity, clinicians can better predict who might be at risk for adverse drug reactions or who might require a dosage adjustment to achieve therapeutic success.
Research and Evidence Strength
The association between specific CYP2D6 variants and drug response is well-established in scientific literature, though the evidence for any single SNP like rs1799972 can be nuanced. While the gene itself is a major focus of clinical pharmacogenetics, the specific impact of rs1799972 is often evaluated as part of a larger haplotype or 'star allele' definition. Current research indicates that while some variants have a clear, high-impact effect on enzyme function, others have more limited or context-dependent associations. The evidence strength for rs1799972 is currently considered limited, meaning that while it is a marker of interest, it may not be the sole determinant of how a patient metabolizes a specific drug. Clinical guidelines, such as those from the Clinical Pharmacogenetics Implementation Consortium (CPIC), emphasize that genotype-predicted phenotypes should be interpreted with caution and integrated with other clinical factors, such as age, liver function, and concurrent medication use, rather than used in isolation.
Population Frequency and Diversity
Genetic variation in CYP2D6 is not distributed equally across the globe. Research has shown that the frequency of various CYP2D6 alleles differs significantly between ancestral groups. For instance, some alleles that result in reduced enzyme function are more common in certain Asian populations, while others are more prevalent in African or European populations. According to data from gnomAD, the minor allele frequency for rs1799972 is approximately 0.33 in populations of African ancestry. This high degree of variability underscores the importance of studying pharmacogenes in diverse populations to ensure that clinical guidelines are accurate and equitable. Because allele frequencies vary, a genotype that is common in one population may be rare in another, which can lead to differences in the prevalence of predicted metabolizer phenotypes across the world. Understanding these population-specific frequencies is a critical step in implementing personalized medicine strategies that are effective for all patients.
What You Can Do With This Information
If you have received information about your CYP2D6 genotype, it is important to view it as one piece of a much larger clinical puzzle. You cannot use this information to diagnose yourself or to make changes to your medication regimen. Pharmacogenetic testing is a tool intended to support, not replace, the professional judgment of your healthcare provider. If you are concerned about how a medication is affecting you, or if you are interested in how your genetics might influence your response to a drug, the best course of action is to have a conversation with your doctor or a clinical pharmacist. They can interpret your results in the context of your specific health history and current prescriptions. Never stop or change the dose of a prescribed medication based on genetic test results without consulting your clinician, as doing so could lead to serious health consequences.
How common is this variant?
The minor allele frequency for rs1799972 is approximately 0.33 in African ancestry populations, though frequencies vary significantly across different global populations.
Frequently asked questions
Does having a specific CYP2D6 genotype mean I will have side effects?
Not necessarily. While your genotype can influence how your body processes certain drugs, side effects are also influenced by your age, diet, other medications you are taking, and your overall health. Genetic testing is only one factor that doctors consider when prescribing medication.
Can I use this genetic information to choose my own medication?
No. You should never use genetic information to select or change your own medication. Always discuss your genetic test results with your doctor or a pharmacist who can interpret them in the context of your specific medical needs.
Is CYP2D6 testing standard for everyone?
CYP2D6 testing is not standard for every patient. It is typically ordered by healthcare providers when they are considering prescribing specific medications that are known to be metabolized by this enzyme, especially if there is a concern about efficacy or side effects.
What is a 'poor metabolizer'?
A poor metabolizer is an individual whose genetic profile results in little to no functional CYP2D6 enzyme activity. This can cause certain drugs to build up in the body, potentially increasing the risk of side effects, or prevent the activation of drugs that require the enzyme to work.
Sources & further reading
Educational information only, last refreshed 10/18/2026. Not medical advice — these associations describe population statistics, not individual predictions.
Curious what your genotype is for rs1799972?
Upload a raw DNA file from 23andMe, AncestryDNA, MyHeritage, or FamilyTreeDNA and see this variant — plus thousands more — interpreted in your full report.
Get my report — $29Related variants in CYP2D6
This variant is a key marker for the CYP2D6*10 allele, which results in reduced enzymatic activity and altered metabolism of various psychiatric and analgesic medications.
This variant defines the CYP2D6*4 non-functional allele, which causes impaired metabolism of numerous clinically prescribed medications including antidepressants, tamoxifen, and codeine.
Defines the CYP2D6*17 allele (p.Thr107Ile), which exhibits reduced enzyme activity towards substrates like codeine and certain antidepressants.
Defines the CYP2D6*29 variant (p.Val338Met) conferring decreased metabolic capacity, primarily observed in populations of African descent.
Promoter variant defining the CYP2D6*41 allele, associated with reduced enzyme expression and decreased metabolic capacity for various drugs.
Defines the CYP2D6*6 deletion variant (1707delT) leading to a premature stop codon and loss of enzyme function.