F13A1 rs1800793: Understanding the Val34Leu Variant
The F13A1 rs1800793 variant, commonly known as Val34Leu, is a genetic change that alters the structure of the factor XIII-A subunit. This variant is known to accelerate the activation of factor XIII, a protein essential for stabilizing blood clots.
What each genotype means
Standard factor XIII activation
This genotype represents the most common form of the F13A1 gene, often referred to as the Val34 allele. Research indicates that individuals with this genotype have standard factor XIII activation rates, which are essential for normal blood clot formation. Studies investigating potential links to cardiovascular or clotting conditions have yielded conflicting results, and it is not considered a major risk factor.
This is the most common genotype in most global populations, though the frequency of the alternative allele varies significantly by ancestry.
Accelerated factor XIII activation
This genotype, often referred to as Val34Leu or V34L, involves one copy of the variant that accelerates the activation of factor XIII. Some research suggests this may alter fibrin clot stability and potentially offer protection against venous thromboembolism, though findings across different studies remain inconsistent. It is not a diagnostic marker, and its clinical significance remains a subject of ongoing research.
Carried by a significant portion of individuals of European ancestry, with a minor allele frequency typically between 0.20 and 0.28, but it is much less common in East Asian populations.
Increased factor XIII activation
This genotype represents the homozygous state for the Leu34 variant, which is associated with faster activation of factor XIII compared to the common G allele. While some studies have explored whether this variant provides protection against conditions like venous thromboembolism or myocardial infarction, the evidence is limited and conflicting. It is not currently used to predict clinical outcomes or guide medical management.
This genotype is less common than the heterozygous state, occurring in roughly 4% to 8% of individuals in European populations and is rare in East Asian populations.
What is the rs1800793 Variant?
The rs1800793 variant, frequently referred to in scientific literature as Val34Leu or V34L, is a single nucleotide polymorphism (SNP) located within the F13A1 gene. This gene is situated on chromosome 6 and provides the instructions for creating the A subunit of factor XIII. The variant involves a specific change in the DNA sequence that results in the substitution of the amino acid valine with leucine at position 34 of the protein. Because this change occurs in a critical region of the protein, it has been the subject of extensive research regarding its potential impact on the body's coagulation system. While it is a well-documented genetic marker, it is important to understand that it represents a common variation rather than a rare, disease-causing mutation.
The Role of the F13A1 Gene
The F13A1 gene is responsible for producing the catalytic A subunit of factor XIII. In the bloodstream, factor XIII circulates as a heterotetramer, consisting of two A subunits and two B subunits. When the body needs to form a stable blood clot, factor XIII is activated by thrombin and calcium. This activated protein acts as a transglutaminase, cross-linking fibrin strands to create a robust, stable mesh that prevents excessive bleeding. Because the Val34Leu variant is located near the activation site of the A subunit, it is hypothesized to influence how quickly this activation process occurs. Research indicates that the presence of the leucine allele can accelerate the activation of factor XIII, which may theoretically alter the structural properties of the resulting fibrin clot.
Research and Clinical Associations
The clinical significance of the Val34Leu variant remains a subject of ongoing scientific debate. Early studies suggested that the variant might offer a protective effect against conditions like venous thromboembolism and myocardial infarction by altering clot stability. However, subsequent research has produced conflicting results, with many large-scale studies failing to find a consistent or strong association between this specific SNP and cardiovascular disease risk. Because the evidence is mixed and often varies between different study populations, it is not currently used as a reliable diagnostic tool for predicting clotting disorders. The scientific community continues to investigate whether this variant interacts with other genetic or environmental factors to influence health outcomes, but it is not considered a primary driver of clinical disease.
Population Frequency
The frequency of the Val34Leu variant varies significantly across different ancestral groups. In European populations, the minor allele frequency is typically observed between 0.20 and 0.28. In contrast, the variant is much less common in East Asian populations, where the frequency is generally reported to be below 0.02. These differences highlight the importance of considering genetic ancestry when interpreting population-level data regarding this variant.
Interpreting Your Genetic Information
If you have received information about your F13A1 genotype, it is important to view it within the context of current scientific understanding. This variant is a common polymorphism, and its presence does not constitute a medical diagnosis or a definitive prediction of health outcomes. Because the research regarding its impact on clotting risk is inconsistent, this information should not be used to make decisions about your health or medical care. If you have concerns about your risk for blood clots or other cardiovascular conditions, the most appropriate step is to consult with a qualified healthcare professional. They can evaluate your personal and family medical history, which are far more significant indicators of health risk than any single genetic variant.
How common is this variant?
The minor allele frequency for rs1800793 is approximately 0.20-0.28 in European populations and less than 0.02 in East Asian populations.
Frequently asked questions
Is the Val34Leu variant a cause of blood clotting disorders?
No, the Val34Leu variant is a common genetic polymorphism and is not considered a primary cause of clotting disorders. While it has been studied for its potential influence on clot stability, it is not a diagnostic marker for disease.
Does this variant mean I am at higher risk for a heart attack?
Research on this topic is conflicting and inconclusive. Many studies have found no significant association between this variant and the risk of heart attack, and it is not used in clinical practice to assess cardiovascular risk.
Should I change my medication based on my F13A1 genotype?
No. You should never change or stop any medication based on genetic test results without first consulting your doctor or pharmacist. Genetic variants like this are not currently used to guide standard anticoagulant dosing.
Why do different studies report different results for this SNP?
Scientific studies often show different results due to variations in study design, the size of the populations studied, and the genetic background of the participants. This is common in complex traits where many factors contribute to health outcomes.
Sources & further reading
Educational information only, last refreshed 9/21/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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The Factor XIII Val34Leu missense variant associated with altered fibrin clot structure and modest protection against venous thromboembolism and myocardial infarction.
Missense alteration (p.Leu34Phe) in coagulation factor XIII A1 subunit modifying clot stability and venous thromboembolism risk.