NAT2 rs1800564: Understanding Your Acetylator Status
The rs1800564 variant is a specific genetic change in the NAT2 gene that influences how the body processes certain medications. It is a key marker used to identify individuals who may be 'slow acetylators,' which can affect how they respond to drugs like isoniazid.
What each genotype means
Normal acetylator status
You carry two copies of the standard G allele at this position, meaning you do not have the slow-acetylator change associated with the NAT2*6 allele. Overall acetylation speed depends on other NAT2 gene variants, but this particular site confers typical enzyme clearance for medications like isoniazid and hydralazine. Always consult your healthcare provider or pharmacist regarding medication dosing and adverse effect risks.
Found in approximately 45% to 55% of individuals of European and South Asian ancestry, and around 60% to 70% of individuals of East Asian ancestry.
Intermediate acetylator status
You carry one copy of the decreased-function A allele defining the NAT2*6 lineage, which reduces NAT2 enzyme stability and drug clearance. Research indicates this single variant often confers intermediate acetylation capacity, though full metabolizer status depends on other variants across your NAT2 gene. If you are prescribed medications cleared by NAT2, such as hydralazine or isoniazid, discuss dosing strategies and monitoring with your clinician or pharmacist.
Carried by approximately 35% to 45% of European and South Asian populations, and roughly 25% to 35% of East Asian populations.
Slow acetylator status
You carry two copies of the decreased-function A allele, which impairs NAT2 protein stability and is strongly associated with a slow acetylator phenotype. Clinical research links slow acetylation to higher drug exposure and an elevated risk of side effects from medications such as hydralazine and isoniazid. Because medication metabolism is influenced by several factors, review any current or future therapies with your doctor or pharmacist.
Occurs in approximately 6% to 12% of individuals of European and South Asian descent, and about 2% to 6% of East Asian individuals.
What is rs1800564?
The rs1800564 variant is a single nucleotide polymorphism (SNP) located within the NAT2 gene. In scientific literature, this specific change is often referred to as c.590G>A, which results in an amino acid substitution known as p.Arg197Gln. This variant is one of several genetic markers that define the NAT2*6 allele. Because the NAT2 gene provides instructions for making an enzyme that breaks down (metabolizes) various drugs and chemicals, changes in this gene can alter the speed at which these substances are cleared from the body. When a person carries this variant, it can reduce the efficiency of the NAT2 enzyme, contributing to a 'slow acetylator' phenotype. This means that for certain medications, the drug may remain in the bloodstream for a longer period than it would in someone with a more active version of the enzyme.
The Role of the NAT2 Gene
The NAT2 gene encodes the N-acetyltransferase 2 enzyme. This enzyme is responsible for a process called acetylation, a chemical reaction that helps the body neutralize and eliminate various drugs, including isoniazid (used for tuberculosis) and hydralazine (used for high blood pressure). The activity level of this enzyme is categorized into three main phenotypes: rapid, intermediate, and slow. Individuals with two functional copies of the gene are typically rapid acetylators, while those with two non-functional or low-activity copies are classified as slow acetylators. Because the NAT2 enzyme is a primary pathway for clearing these specific medications, the genetic variants an individual inherits directly dictate their metabolic capacity. Understanding this gene is a cornerstone of pharmacogenomics, the study of how genes affect a person's response to drugs.
Research and Clinical Associations
Research has consistently linked the slow acetylator phenotype—often determined by variants like rs1800564—to an increased risk of side effects when taking certain medications. For example, individuals who are slow acetylators may have higher levels of isoniazid in their blood, which has been associated with a greater risk of drug-induced liver injury. While the evidence linking specific genotypes to these outcomes is strong in the context of clinical pharmacology, it is important to note that genetic testing is only one piece of the puzzle. Other factors, such as age, liver health, and concurrent use of other medications, also play significant roles in how a person responds to treatment. Clinical guidelines, such as those from the Clinical Pharmacogenetics Implementation Consortium (CPIC), provide recommendations on how to use this genetic information to adjust dosing for patients to improve safety and efficacy.
Population Frequency
The frequency of the rs1800564 variant varies significantly across different global populations. In European and South Asian populations, the minor allele frequency (MAF) is typically observed between 0.25 and 0.35. In East Asian populations, the frequency is generally lower, ranging from approximately 0.15 to 0.25. These differences in allele frequency contribute to the observed variations in the prevalence of the slow acetylator phenotype across different ethnic groups. Because these variants are inherited, the likelihood of being a slow acetylator is often higher in populations where these specific NAT2 alleles are more common.
What You Can Do With This Information
If you have received information about your NAT2 genotype, it is important to view it as a tool for communication with your healthcare provider rather than a medical diagnosis. Genetic variants do not determine your health outcomes in isolation; they simply provide information about how your body might process specific substances. If you are prescribed medications that are known to be metabolized by the NAT2 enzyme, such as isoniazid, you should discuss your genetic profile with your doctor or pharmacist. They can interpret these results in the context of your overall health and determine if a dosage adjustment or closer monitoring is appropriate for you. Never make changes to your prescribed medication regimen based on genetic test results without consulting a qualified medical professional.
How common is this variant?
The rs1800564 variant has a minor allele frequency of approximately 0.25-0.35 in European and South Asian populations, and 0.15-0.25 in East Asian populations.
Frequently asked questions
What does it mean to be a 'slow acetylator'?
A slow acetylator is someone whose body breaks down certain drugs more slowly than average due to reduced activity of the NAT2 enzyme. This can lead to higher concentrations of the drug in the blood, which may increase the risk of side effects.
Does having the A/A genotype mean I will have side effects?
Not necessarily. While the A/A genotype is associated with the slow acetylator phenotype, whether you experience side effects depends on many factors, including the specific drug, the dosage, and your overall health. Always consult your doctor regarding your specific risks.
Should I get tested for NAT2 variants?
Genetic testing for NAT2 is typically performed in a clinical setting when a doctor needs to determine the best dosage for a specific medication. You should discuss the necessity of such testing with your healthcare provider.
Can I change my acetylator status?
No, your NAT2 genotype is inherited and cannot be changed. However, knowing your status allows your healthcare team to manage your medication dosages more effectively to ensure safety.
Sources & further reading
Educational information only, last refreshed 10/17/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Coding variant c.481C>T (p.Leu161Leu) serving as a diagnostic marker for several NAT2 slow acetylator haplotypes, including *5.
Coding variant c.857G>A (p.Gly286Glu) defining the NAT2*14 allele (often associated with slow acetylation).
Synonymous variant (282C>T) associated with the NAT2*6 allele, contributing to slow acetylator status.
Missense variant (590G>A) defining the NAT2*6A allele, associated with slow acetylator phenotype.
Synonymous polymorphism (857G>A) representing the defining mutation of the slow acetylator NAT2*7 allele.
This variant (c.590G>A, p.Arg197Gln) is a well-characterized slow acetylator allele in the NAT2 gene, influencing the metabolism of drugs like isoniazid.