F2 rs1799963: Understanding the Prothrombin G20210A Variant
The F2 rs1799963 variant, commonly known as Prothrombin G20210A, is a genetic change in the prothrombin gene associated with increased levels of the prothrombin protein. This variant is recognized for its role in increasing the risk of venous thromboembolism, a condition characterized by the formation of blood clots in the veins.
What each genotype means
Typical prothrombin risk profile
This is the most common genotype and is considered the reference or normal state for the F2 gene. Individuals with this genotype do not carry the G20210A mutation associated with increased prothrombin levels and elevated venous thromboembolism risk.
Carried by the vast majority of the population, with the variant allele present in only about 2-3% of people of European ancestry.
Increased venous thrombosis risk
This genotype, often called heterozygous for the G20210A mutation, is associated with a 2- to 3-fold increased risk of a first venous thromboembolism. Research indicates that women with this genotype who use hormonal contraceptives face a significantly higher risk of thrombosis compared to non-carriers. Please discuss any concerns regarding medication or lifestyle factors with your clinician or pharmacist.
Carried by approximately 2% to 3% of individuals of European ancestry; it is less common in other populations.
Elevated prothrombin risk profile
This genotype represents a homozygous state for the G20210A mutation, which can lead to higher prothrombin levels in the blood. While this is associated with an increased susceptibility to venous thromboembolism, clinical manifestations can vary significantly between individuals. Please consult with a healthcare provider to discuss your personal health history and any necessary preventative strategies.
This is a rare genotype, occurring much less frequently than the heterozygous state in the general population.
What is the rs1799963 Variant?
The rs1799963 variant, frequently referred to as the G20210A mutation, is a specific change in the DNA sequence of the F2 gene. Located on chromosome 11, this variant involves the substitution of a single nucleotide, where adenine (A) replaces guanine (G) at position 20210 within the 3'-untranslated region of the gene. This region is critical because it helps regulate the stability and expression of the messenger RNA produced by the gene. By altering this regulatory site, the variant leads to increased production of prothrombin, a protein essential for blood clotting. Because it affects how the gene is expressed rather than the structure of the protein itself, it is often studied in the context of inherited thrombophilia, a condition that predisposes individuals to abnormal blood clotting.
The Role of the F2 Gene
The F2 gene provides the instructions for the body to produce a protein called prothrombin, also known as coagulation factor II. Prothrombin is synthesized primarily in the liver and circulates in the bloodstream as an inactive precursor. When an injury occurs that damages blood vessels, a complex cascade of chemical reactions is triggered, converting prothrombin into its active form, thrombin. Thrombin then acts as a key enzyme to convert fibrinogen into fibrin, which forms the structural mesh of a blood clot. Because prothrombin is central to the coagulation cascade, the amount of this protein in the blood must be tightly regulated. Variants like rs1799963 can disrupt this balance, leading to higher-than-normal levels of prothrombin, which may shift the body's coagulation system toward a state that is more prone to forming clots.
Research and Clinical Associations
Research has consistently identified rs1799963 as a significant genetic risk factor for venous thromboembolism (VTE), which includes conditions like deep vein thrombosis (DVT) and pulmonary embolism (PE). It is considered the second most common inherited thrombophilia after Factor V Leiden. Studies have shown that individuals carrying the A allele have higher prothrombin activity compared to those with the common GG genotype. The evidence for this association is considered moderate to strong in clinical literature. Furthermore, research indicates that the risk associated with this variant can be compounded by external factors. For instance, studies have observed that women who carry the A allele and use hormonal contraceptives face a significantly higher risk of developing DVT compared to non-carriers. While the association with venous clotting is well-documented, its link to arterial diseases, such as myocardial infarction, remains a subject of ongoing investigation with mixed results across different populations.
Navigating Your Genetic Information
Understanding your status for the rs1799963 variant provides insight into your genetic predisposition for clotting, but it is not a diagnostic tool for predicting a specific medical event. Genetic risk is only one piece of a larger puzzle that includes lifestyle, environment, and other health factors. If you are concerned about your risk of blood clots or are considering medical interventions, it is essential to discuss your genetic results with a qualified healthcare provider or a genetic counselor. They can help interpret these findings in the context of your personal and family medical history. Never use genetic information to make decisions about starting, stopping, or changing medications, such as anticoagulants or hormonal contraceptives, without direct guidance from your clinician or pharmacist. They are the only ones who can provide personalized medical advice based on your complete health profile.
How common is this variant?
The A allele of the rs1799963 variant is relatively uncommon, with a frequency of approximately 2% in European populations. Its prevalence varies significantly across different global ancestries.
Frequently asked questions
Is the F2 G20210A variant the same as Factor V Leiden?
No, they are distinct genetic variants. Both are inherited thrombophilias that increase the risk of blood clots, but they occur in different genes and involve different mechanisms in the blood clotting cascade.
Does having the A allele mean I will definitely develop a blood clot?
No, having the variant does not guarantee that you will develop a blood clot. It is a risk factor, meaning it increases the likelihood, but many people with the variant never experience a thrombotic event.
Should I get tested for the F2 mutation?
Genetic testing for this variant is typically recommended by doctors only in specific clinical situations, such as after a personal or family history of unexplained blood clots. You should discuss the necessity of testing with your healthcare provider.
Can I change my diet to lower my prothrombin levels?
There is no specific diet proven to counteract the effects of the F2 G20210A variant on prothrombin levels. Always consult with a doctor or a registered dietitian before making significant changes to your diet for health reasons.
Sources & further reading
Educational information only, last refreshed 10/8/2026. Not medical advice — these associations describe population statistics, not individual predictions.
Curious what your genotype is for rs1799963?
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 — $29