What you carry at this position in your DNA and what research says about it.
Blood Clot Risk: 9/10 evidence, 26 publications.
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Sample genotype (not yours): T/T
Significantly Higher Blood Clot Risk
Carrying two copies of the T allele is associated with a significantly higher risk of venous blood clots and elevated LDL cholesterol. It also substantially increases the likelihood of developing a dry cough when taking enalapril or other ACE inhibitors.
What this genotype means: Significantly higher risk of venous thromboembolism; Elevated LDL cholesterol and triglycerides; Increased risk of dry cough when taking ACE inhibitors.
Sample genotype (not yours): G/G
Lower Risk of Blood Clots
Carrying two copies of the G allele is associated with a typical, lower risk of developing blood clots and a typical risk of high blood pressure. It also correlates with a lower likelihood of developing a dry cough when taking certain blood pressure medications.
What this genotype means: Typical, lower risk of venous thromboembolism; Lower baseline LDL cholesterol; Typical risk of high blood pressure.
Sample genotype (not yours): T/G
Elevated Risk of Blood Clots
Carrying one copy of the T allele is linked to a higher risk of venous blood clots and slightly elevated LDL cholesterol. It may also slightly lower susceptibility to high blood pressure.
What this genotype means: Moderately increased risk of venous thromboembolism; Slightly elevated LDL cholesterol levels; Slightly lower susceptibility to high blood pressure.
Gene function and biological role
Gene Function: The ABO gene encodes the glycosyltransferase enzyme responsible for determining an individual's ABO blood group [1]. Beyond defining blood types, this gene plays a critical role in cardiovascular health by influencing the levels of various plasma proteins, including von Willebrand factor and factor VIII [2]. These proteins are essential components of the blood clotting cascade, meaning variations in the ABO gene directly affect clotting tendency [2]. Additionally, the ABO locus has been linked to systemic inflammation, cell adhesion, and the activity of angiotensin-converting enzyme [3]. Through these diverse pathways, the gene impacts the risk of thrombosis, heart disease, and even response to certain medications [4].
Variant Impact: The rs495828 variant is an intergenic single nucleotide polymorphism located near the ABO gene locus. This genetic change acts as a strong marker for the A and O blood groups, with the G allele correlating with O and B types, and the T allele with A and AB types [1]. It significantly influences the expression and activity of angiotensin-converting enzyme in the blood. By altering enzyme activity and blood group antigen expression, the variant affects cellular adhesion and inflammatory pathways [3]. These downstream physiological changes explain its strong association with venous thromboembolism and blood pressure regulation [2]. It also serves as a key predictor for adverse drug reactions to specific antihypertensive therapies [4].
Key Insight: This variant near the ABO gene not only influences your blood type but also acts as a major genetic driver of blood clot risk and how you react to common blood pressure medications.
Location: ABO. Chromosome 9 · 9q34.2 · 133.3 Mb
Estimated prevalence by population
Global 3.8%; European 4.8%; African 1.9%; East Asian 4.0%; South Asian 2.6%; Americas 2.9%; Ashkenazi 4.7%; Finnish 5.1%; Middle Eastern 4.0%; Amish 23.6%.
Estimated TT genotype frequency.
Global 30.5%; European 34.2%; African 23.6%; East Asian 32.1%; South Asian 26.9%; Americas 28.2%; Ashkenazi 33.9%; Finnish 34.9%; Middle Eastern 32.1%; Amish 50.0%.
Estimated TG genotype frequency.
Global 65.7%; European 61.1%; African 74.6%; East Asian 63.9%; South Asian 70.5%; Americas 68.9%; Ashkenazi 61.4%; Finnish 60.0%; Middle Eastern 63.9%; Amish 26.5%.
Estimated GG genotype frequency.
Showing effects for T/T genotype
Cardiovascular & Metabolic
Coagulation & Clotting
Venous Thromboembolism. Evidence: 4/10. Source: PMID 22672568. ~1.65x Higher Risk.
Lipids & Cholesterol
LDL Cholesterol. Evidence: 8/10. Source: PMID 30698716. Increased Levels.
Hypertension
Hypertension. Evidence: 6/10. Source: PMID 22258027. Lower Risk.
Blood Cell & Iron Traits
Hemoglobin Levels. Evidence: 9/10. Source: PMID 20139978. Slightly Lower.
Pharmacogenomics
Cardiovascular Drug Response
ACE Inhibitor Cough. Evidence: 5/10. Source: PMID 24743543. Increased Risk.
Showing effects for G/G genotype
Venous Thromboembolism. Evidence: 4/10. Source: PMID 22672568. Typical Risk.
LDL Cholesterol. Evidence: 8/10. Source: PMID 30698716. Typical Levels.
Hypertension. Evidence: 6/10. Source: PMID 22258027. Typical Risk.
Hemoglobin Levels. Evidence: 9/10. Source: PMID 20139978. Slightly Higher.
ACE Inhibitor Cough. Evidence: 5/10. Source: PMID 24743543. Typical Risk.
Showing effects for T/G genotype
Venous Thromboembolism. Evidence: 4/10. Source: PMID 22672568. Increased Risk.
LDL Cholesterol. Evidence: 8/10. Source: PMID 30698716. Slightly Increased.
Hypertension. Evidence: 6/10. Source: PMID 22258027. Slightly Lower Risk.
Hemoglobin Levels. Evidence: 9/10. Source: PMID 20139978. Typical.
What this genotype means for the people who carry it
Sample genotype: TT (Homozygous)
Possessing two copies of the T allele is associated with the highest relative risk for several cardiovascular and respiratory traits at this locus. Clinical studies have demonstrated a significantly elevated risk of venous thromboembolism, with odds ratios substantially higher than the common G/G genotype [1]. This genotype is also strongly linked to higher LDL cholesterol and triglyceride levels, which can impact long-term arterial health [2]. When treated with the blood pressure medication enalapril, individuals with this profile have a pronounced risk of developing an irritating dry cough [3]. Blood pressure runs the other way at this variant: the T allele tracks lower plasma ACE activity and a lower risk of developing high blood pressure [4]. Beyond cardiovascular factors, some research links this genotype to a higher susceptibility to asthma and endometriosis [5]. Hemoglobin and hematocrit levels are typically at their lowest with this genetic combination [6]. These combined factors highlight the importance of proactive cardiovascular monitoring and lifestyle management.
Significantly higher risk of venous thromboembolism; Elevated LDL cholesterol and triglycerides; Increased risk of dry cough when taking ACE inhibitors.
Sample genotype: GG (Homozygous)
Two copies of the common G allele provide a baseline level of cardiovascular health. Research indicates that this genetic profile is associated with a lower risk of venous thromboembolism compared to carrying the T allele [1]. Additionally, these individuals tend to have lower LDL cholesterol levels and are less likely to experience a dry cough as a side effect of ACE inhibitor medications like enalapril [2]. Blood pressure risk is typical for this genotype; it is the T allele, not G, that tracks lower ACE activity and lower hypertension risk [3]. On the other hand, the G allele is associated with slightly higher hemoglobin and hematocrit levels, which are typical markers of red blood cell concentration [4]. These hematological traits are generally within normal physiological ranges and do not pose health concerns. Overall, this genotype represents the most common genetic baseline across global populations.
Typical, lower risk of venous thromboembolism; Lower baseline LDL cholesterol; Typical risk of high blood pressure.
Sample genotype: TG (Heterozygous)
A single copy of the T allele introduces a moderate shift in cardiovascular and metabolic risk profiles. Studies have shown that carrying this variant increases the odds of developing venous blood clots, also known as venous thromboembolism [1]. It is also associated with slightly higher levels of LDL cholesterol and apolipoprotein B, which are key markers of cardiovascular health [2]. Blood pressure may run slightly lower than the common G/G baseline, since the T allele tracks reduced ACE activity [3]. While the risk of enalapril-induced cough is not as high as in those with two copies of the T allele, some increased susceptibility remains [4]. Furthermore, this genetic profile is linked to slightly lower hemoglobin levels, though usually still within normal limits [5]. Managing lifestyle factors like diet, exercise, and avoiding prolonged immobility can help mitigate these elevated risks.
Moderately increased risk of venous thromboembolism; Slightly elevated LDL cholesterol levels; Slightly lower susceptibility to high blood pressure.
Variants with shared genetic architecture
rs507666 · ABO Gene · Chr 9 · Heart Disease Risk
rs550057 · ABO Gene · Chr 9 · COVID-19 Severity
rs505922 · ABO Gene · Chr 9 · Blood Type Disease Risk
Influence of ABO genotype and phenotype on angiotensin-converting enzyme plasma activity.
Multiancestry Genome-Wide Association Study of Lipid Levels Incorporating Gene-Alcohol Interactions.
A common variant of the ABO gene protects against hypertension in a Spanish population.
Genome-wide association study of hematological and biochemical traits in a Japanese population.
Content updated August 2026.
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