F13A1 rs1800791: What Your Genotype Means
The rs1800791 variant in the F13A1 gene is a common genetic change that alters the structure of coagulation factor XIII. Research has investigated its potential role in modifying blood clot stability and its association with the risk of venous thromboembolism and myocardial infarction.
What each genotype means
Typical clot stabilization
This genotype represents the most common form of the F13A1 gene in many populations. It is associated with standard production of the factor XIII A subunit, which helps stabilize blood clots after injury.
This is the most frequent genotype, carried by the majority of individuals in most global populations.
Modified clot stability profile
Individuals with this genotype carry one copy of the variant associated with the p.Leu34Phe alteration. Research suggests this change may influence the rate at which fibrin clots are stabilized, though the clinical significance regarding venous thromboembolism risk remains a subject of ongoing study.
This heterozygous genotype is common, appearing in approximately 30-40% of individuals of European ancestry.
Alternative clot stability profile
This genotype results in the p.Leu34Phe alteration on both copies of the F13A1 gene. While this variant is studied for its potential role in modifying clot structure and venous thromboembolism risk, it is not considered a primary cause of factor XIII deficiency; please consult a clinician if you have concerns about personal or family history of clotting or bleeding.
This genotype is less common, found in roughly 5-10% of individuals of European ancestry.
Understanding the rs1800791 Variant
The genetic variant rs1800791, often referred to in scientific literature as the Val34Leu or V34L polymorphism, is a single nucleotide change located within the F13A1 gene. This gene provides instructions for creating the A subunit of coagulation factor XIII, a critical protein in the final stages of the blood coagulation cascade. The variant involves a substitution where the amino acid valine is replaced by leucine at position 34 of the protein. Because this position is located near a thrombin activation site, the change is thought to influence how quickly factor XIII is activated in the body. This variant is considered a common polymorphism, meaning it occurs frequently in the general population rather than being a rare mutation associated with severe, early-onset disease.
The Role of F13A1 in Blood Clotting
Factor XIII acts as a transglutaminase, an enzyme that serves as the final step in stabilizing blood clots. Once activated by thrombin and calcium, it creates cross-links between fibrin molecules, which reinforces the structure of the clot and makes it more resistant to premature breakdown. By strengthening the fibrin mesh, factor XIII ensures that clots are stable enough to prevent excessive bleeding after an injury. Because the rs1800791 variant alters the amino acid sequence near the activation site, it has been the subject of extensive study to determine if it changes the rate at which factor XIII is activated or the final architecture of the fibrin clot. Understanding these functional changes is important for researchers studying the complex balance between preventing bleeding and avoiding unwanted blood clots.
Research Associations and Evidence
Scientific research into rs1800791 has primarily focused on its association with thrombotic conditions, such as venous thromboembolism and myocardial infarction. Some studies have suggested that the variant may have a protective effect, potentially by influencing clot structure in a way that makes them easier to break down or less likely to form in harmful locations. However, the evidence remains mixed and is often described as limited or context-dependent. For example, some meta-analyses have indicated a protective association, while other studies have found no significant impact or have noted that the effect may vary based on other factors, such as fibrinogen levels or specific environmental triggers. Because cardiovascular health is influenced by many genetic and lifestyle factors, this variant is considered one of many contributors rather than a primary cause of disease.
Population Frequency
The rs1800791 variant is relatively common, with a minor allele frequency typically reported between 0.20 and 0.25 in European populations. This means that a significant portion of the population carries at least one copy of the variant allele, making it a widespread genetic feature rather than an anomaly.
Interpreting Your Genetic Information
It is important to understand that genetic variants like rs1800791 represent statistical associations observed in large research studies, not individual medical predictions. Having a specific genotype does not mean you will or will not develop a particular health condition. Cardiovascular health is complex, involving a combination of genetics, diet, exercise, and other environmental factors. If you are concerned about your risk for blood clots or cardiovascular disease, you should consult with a healthcare professional who can evaluate your personal and family medical history. Never use genetic information to make decisions about medications or treatments without discussing them with your doctor or pharmacist, as they can provide guidance based on your complete clinical profile.
How common is this variant?
The rs1800791 variant is common, with a minor allele frequency of approximately 0.20 to 0.25 in European populations.
Frequently asked questions
Is rs1800791 a cause of blood clots?
No, rs1800791 is a common genetic variant associated with variations in clot structure, not a direct cause of clotting disorders. Most people with this variant live healthy lives without experiencing abnormal clotting.
Should I get tested for this variant?
Routine testing for this variant is not typically recommended for the general public. Genetic associations are complex, and clinical decisions are best made based on your overall health and medical history.
Does this variant affect my medication?
There is no standard clinical guidance suggesting this variant requires specific medication adjustments. Always discuss any concerns about your medications with your doctor or pharmacist.
What does 'protective effect' mean in this context?
In research, a protective effect suggests that a specific genotype is statistically associated with a lower risk of a condition compared to other genotypes. It does not guarantee immunity from the condition.
Sources & further reading
Educational information only, last refreshed 10/16/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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The Val34Leu missense change accelerates factor XIII activation, imparting protection against venous thromboembolism while altering fibrin clot stability.
The Factor XIII Val34Leu missense variant associated with altered fibrin clot structure and modest protection against venous thromboembolism and myocardial infarction.