What you carry at this position in your DNA and what research says about it.
Blood Clot Risk: 9/10 evidence, 24 publications.
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Sample genotype (not yours): A/A
Higher Risk of Blood Clots
Carrying two copies of the A allele is associated with having a non-O blood type. This genotype leads to significantly higher levels of clotting factors and an increased risk of blood clots.
What this genotype means: Significantly higher levels of von Willebrand factor and factor VIII; Increased risk of deep vein thrombosis and pulmonary embolism; Higher susceptibility to severe respiratory infections.
Sample genotype (not yours): A/G
Slightly Increased Risk of Blood Clots
Carrying one copy of the A allele is associated with having a non-O blood type. This genotype leads to moderately higher levels of clotting factors and a slightly elevated risk of blood clots.
What this genotype means: Moderately elevated levels of key blood clotting factors; Slightly increased risk of venous thromboembolism; Slightly higher susceptibility to severe respiratory complications.
Sample genotype (not yours): G/G
Lower Risk of Blood Clots
Carrying two copies of the G allele is strongly associated with having blood type O. This genotype is linked to lower levels of clotting factors and a reduced risk of venous thromboembolism.
What this genotype means: Lower circulating levels of von Willebrand factor and factor VIII; Reduced risk of deep vein thrombosis and pulmonary embolism; Lower susceptibility to severe respiratory infections and pancreatic cancer.
Gene function and biological role
Gene Function: The ABO gene encodes the glycosyltransferase enzymes responsible for determining an individual's ABO blood group [1]. These enzymes transfer specific sugar molecules to the H antigen on the surface of red blood cells and other tissues [1]. Depending on which functional enzymes are produced, a person will have blood type A, B, AB, or O [1]. Beyond determining blood type, the ABO gene plays a critical role in regulating blood coagulation factors, such as von Willebrand factor and factor VIII [2]. Consequently, variations in this gene are major genetic determinants of cardiovascular risk, blood clotting disorders, and susceptibility to certain infectious diseases [2].
Variant Impact: The rs687289 variant is an intron variant within the ABO gene that serves as a strong genetic tag for blood type [1]. The G allele is highly correlated with the O blood type, which is characterized by a natural lack of active A or B glycosyltransferase enzymes [1]. Conversely, the A allele is associated with non-O blood types (A, B, or AB) [1]. This genetic difference directly influences the plasma levels of key clotting proteins, including von Willebrand factor and coagulation factor VIII [3]. As a result, this single nucleotide change is one of the most powerful genetic predictors of venous thromboembolism and other vascular phenotypes [3].
Key Insight: This genetic variant is a highly accurate proxy for your ABO blood group, which directly dictates how sticky your blood is and how easily it clots.
Location: ABO. Chromosome 9 · 9q34.2 · 133.3 Mb
Estimated prevalence by population
Global 14.4%; European 11.8%; African 17.8%; East Asian 14.9%; South Asian 19.3%; Americas 7.9%; Ashkenazi 18.8%; Finnish 21.2%; Middle Eastern 11.1%; Amish 42.2%.
Estimated AA genotype frequency.
Global 46.3%; European 45.1%; African 48.8%; East Asian 47.4%; South Asian 49.3%; Americas 40.4%; Ashkenazi 49.1%; Finnish 49.7%; Middle Eastern 44.4%; Amish 45.5%.
Estimated AG genotype frequency.
Global 39.3%; European 43.1%; African 33.4%; East Asian 37.7%; South Asian 31.4%; Americas 51.6%; Ashkenazi 32.1%; Finnish 29.1%; Middle Eastern 44.4%; Amish 12.3%.
Estimated GG genotype frequency.
Showing effects for A/A genotype
Cardiovascular & Metabolic
Coagulation & Clotting
Venous Thromboembolism. Evidence: 9/10. Source: PMID 31420334. Higher Risk.
Factor VIII Levels. Evidence: 8/10. Source: PMID 20231535. Higher Levels.
Deep Vein Thrombosis. Evidence: 8/10. Source: PMID 39789286. Higher Risk.
Von Willebrand Factor. Evidence: 6/10. Source: PMID 30586737. Higher Levels.
Immunity & Inflammation
Infection Susceptibility & Resistance
COVID-19 Severity. Evidence: 5/10. Source: PMID 35848942. ~1.24x Higher Risk.
Cancer & Oncology
Gastrointestinal Cancers
Pancreatic Cancer. Evidence: 6/10. Source: PMID 25086665. Higher Risk.
Showing effects for A/G genotype
Venous Thromboembolism. Evidence: 9/10. Source: PMID 31420334. Slightly Higher Risk.
Factor VIII Levels. Evidence: 8/10. Source: PMID 20231535. Moderately Higher.
Deep Vein Thrombosis. Evidence: 8/10. Source: PMID 39789286. Slightly Higher Risk.
Von Willebrand Factor. Evidence: 6/10. Source: PMID 30586737. Moderately Higher.
COVID-19 Severity. Evidence: 5/10. Source: PMID 35848942. Slightly Higher Risk.
Pancreatic Cancer. Evidence: 6/10. Source: PMID 25086665. Slightly Higher Risk.
Showing effects for G/G genotype
Venous Thromboembolism. Evidence: 9/10. Source: PMID 31420334. Lower Risk.
Factor VIII Levels. Evidence: 8/10. Source: PMID 20231535. Typical Levels.
Deep Vein Thrombosis. Evidence: 8/10. Source: PMID 39789286. Lower Risk.
Von Willebrand Factor. Evidence: 6/10. Source: PMID 30586737. Typical Levels.
COVID-19 Severity. Evidence: 5/10. Source: PMID 35848942. Typical Risk.
Pancreatic Cancer. Evidence: 6/10. Source: PMID 25086665. Lower Risk.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Inheriting two copies of the A allele strongly correlates with non-O blood types, such as A, B, or AB [1]. This genetic profile results in higher circulating levels of von Willebrand factor and coagulation factor VIII, which are key proteins involved in blood clotting [2]. Because these clotting factors are elevated, individuals with this genotype have a significantly higher risk of developing venous thromboembolism and deep vein thrombosis [2]. Additionally, large-scale studies have linked this genotype to an increased risk of severe respiratory complications and hospitalization during certain viral infections, such as COVID-19 [3]. Research also suggests a moderate increase in susceptibility to pancreatic cancer compared to those with the protective G/G genotype [4]. Managing cardiovascular health through lifestyle choices is particularly beneficial for individuals with this genetic profile.
Significantly higher levels of von Willebrand factor and factor VIII; Increased risk of deep vein thrombosis and pulmonary embolism; Higher susceptibility to severe respiratory infections.
Sample genotype: AG (Heterozygous)
Carrying one copy of the A allele and one copy of the G allele typically corresponds to a non-O blood type, meaning the body produces active glycosyltransferase enzymes [1]. This heterozygous state results in intermediate to high levels of essential blood clotting proteins, specifically von Willebrand factor and factor VIII [2]. Consequently, there is a moderate increase in the risk of developing venous thromboembolism and deep vein thrombosis compared to the protective G/G genotype [2]. Studies also indicate a slightly elevated risk of severe respiratory symptoms and complications during viral infections like COVID-19 [3]. Furthermore, this genetic combination is associated with a mild increase in pancreatic cancer susceptibility [4]. Maintaining an active lifestyle and staying hydrated during long travel can help mitigate these moderate vascular risks.
Moderately elevated levels of key blood clotting factors; Slightly increased risk of venous thromboembolism; Slightly higher susceptibility to severe respiratory complications.
Sample genotype: GG (Homozygous)
Carrying two copies of the G allele is a highly reliable genetic indicator of having blood type O [1]. Because blood type O lacks active A and B glycosyltransferase enzymes, individuals with this genotype naturally maintain lower circulating levels of von Willebrand factor and coagulation factor VIII [2]. These lower protein levels result in a highly protective effect against abnormal blood clots, significantly reducing the risk of deep vein thrombosis and venous thromboembolism [2]. Furthermore, this genotype is associated with a lower risk of severe respiratory failure and hospitalization when exposed to certain viral infections, including COVID-19 [3]. Research also demonstrates a reduced susceptibility to pancreatic cancer compared to individuals carrying the A allele [4]. While this profile is highly protective against clotting, standard cardiovascular health practices remain important.
Lower circulating levels of von Willebrand factor and factor VIII; Reduced risk of deep vein thrombosis and pulmonary embolism; Lower susceptibility to severe respiratory infections and pancreatic cancer.
Variants with shared genetic architecture
rs507666 · ABO Gene · Chr 9 · Heart Disease Risk
rs550057 · ABO Gene · Chr 9 · COVID-19 Severity
rs495828 · ABO Gene · Chr 9 · Blood Clot Risk
Detailed stratified GWAS analysis for severe COVID-19 in four European populations.
Genome-wide association study identifies multiple susceptibility loci for pancreatic cancer.
Content updated August 2026.
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