Factor V Leiden rs6025 and Blood Clot Risk Explained
- 6 days ago
- 8 min read
Updated: 5 days ago
Factor V Leiden rs6025 is a well-established variant in the F5 gene that affects how the body regulates blood clotting [R]. People with one or two copies of the variant have an increased susceptibility to venous blood clots, particularly deep vein thrombosis and pulmonary embolism [R].
Your result for this SNP do not mean that a blood clot is present or that one will definitely develop. Many people who carry Factor V Leiden never experience thrombosis, and individual risk depends heavily on age, family history, medical history, medications, pregnancy, surgery, immobility, and other genetic or acquired factors [R].
What is Factor V Leiden rs6025?
Factor V Leiden is a variant in the F5 gene. This gene provides instructions for producing coagulation factor V, a protein that helps the body form blood clots after an injury [R, R].
Normal clotting is essential. It prevents excessive bleeding when a blood vessel is damaged. The body must also be able to slow the clotting process once the damaged area has been stabilized. The rs6025 variant changes the structure of factor V in a way that makes it more resistant to normal deactivation [R]. This can keep clotting activity elevated for longer than intended and shift the balance toward an increased tendency to form abnormal clots.
Factor V Leiden is one of the most extensively studied inherited thrombophilia variants, but it has incomplete penetrance. This means that not everyone who carries the variant develops a clot.
How factor V normally regulates clotting
Factor V acts as a cofactor in the coagulation cascade. Once activated, it helps convert prothrombin into thrombin [R, R]. Thrombin then supports the formation of fibrin, which helps create a stable blood clot. The body controls this process partly through activated protein C, often abbreviated as APC. Activated protein C cuts and inactivates factor Va after it has performed its role [R, R].
Factor V Leiden alters one of the sites involved in this process. Activated protein C cannot deactivate the altered protein as efficiently, producing what is known as activated protein C resistance [R]. Factor Va may therefore remain active for longer, contributing to increased thrombin formation and greater susceptibility to venous thrombosis [R].
What a Factor V Leiden rs6025 result can show
Consumer raw DNA files may display rs6025 using the forward genomic orientation. In that format, the three possible genotype results are:
Genotype | Result |
CC | The Factor V Leiden variant was not detected at rs6025. |
CT | One copy of the Factor V Leiden variant was detected. |
TT | Two copies of the Factor V Leiden variant were detected. |
One copy is described as heterozygous Factor V Leiden, while two copies are described as homozygous Factor V Leiden [R].
Research consistently shows that carrying one copy is associated with a several-fold increase in relative venous thrombosis risk compared with not carrying the variant [R]. Two copies are considerably less common and are generally associated with substantially greater susceptibility [R].
These descriptions should not be interpreted as exact personal-risk percentages. Published estimates differ across populations, study designs, age groups, and clinical circumstances.
A CC result also does not mean that a person cannot develop a blood clot. It only means that Factor V Leiden was not detected at this particular marker. Many other genetic and non-genetic factors can contribute to thrombosis.
Why different sources may show different letters
Factor V Leiden can appear under several names:
rs6025
F5 c.1601G>A
C>T in forward genomic notation
p.Arg534Gln using current protein numbering
p.Arg506Gln or R506Q using historical numbering
G1691A in older publications
These names can look as though they describe different findings, but they refer to the same Factor V Leiden variant.
The apparent C/T versus G/A difference results from strand orientation and the type of genetic notation being used. Consumer raw DNA files may show the genomic forward-strand letters, while clinical publications frequently use the F5 transcript orientation.
This is one reason manual raw DNA interpretation can become confusing. The allele letters must be matched to the correct strand and reference notation before a result is interpreted.
Factor V Leiden and venous blood clots
The strongest and most established association is with venous thromboembolism, commonly shortened to VTE [R].
Venous thromboembolism includes two closely connected conditions:
Deep vein thrombosis
A deep vein thrombosis, or DVT, is a clot that forms in a deep vein [R]. It most often occurs in the leg but can also develop in the arm or another part of the body.
Possible symptoms include [R]:
swelling in one limb
unexplained pain or tenderness
warmth
redness or discoloration
Some deep vein thromboses produce few or no noticeable symptoms.
Pulmonary embolism
A pulmonary embolism, or PE, can occur when part of a clot breaks away and travels to the lungs [R].
Possible symptoms include [R]:
sudden difficulty breathing
chest pain that worsens with a deep breath or coughing
a rapid or irregular heartbeat
coughing up blood
lightheadedness or fainting
Possible pulmonary embolism symptoms require immediate medical assessment. Genetic data cannot determine whether a clot is currently present. DVT and pulmonary embolism require appropriate clinical evaluation and imaging.
Does Factor V Leiden cause heart attacks or strokes?
Most heart attacks and common ischemic strokes involve clots forming in or travelling through arteries, where the underlying mechanisms often include atherosclerosis, plaque rupture, platelet activation, blood pressure, and other cardiovascular factors [R]. Some studies have investigated possible associations between Factor V Leiden and arterial events. The results are less consistent, and any association appears much weaker than the established connection with venous thromboembolism.
Factor V Leiden should not be described broadly as a heart attack gene or stroke gene. Its clearest relevance is to conditions such as deep vein thrombosis and pulmonary embolism.
Why the same genotype can have different meanings
Factor V Leiden changes genetic susceptibility, but it does not act alone.
Someone with the variant and no additional risk factors may never develop thrombosis. The same genotype may carry greater practical importance in a person who has experienced a previous clot, has a strong family history, is recovering from major surgery, or has several acquired risk factors.
Factors that may influence venous clot risk include [R]:
previous deep vein thrombosis or pulmonary embolism
a first-degree relative with venous thrombosis
increasing age
major surgery
serious injury
hospitalization
prolonged immobility
a leg cast
long-distance travel
pregnancy
the postpartum period
estrogen-containing medication
obesity
smoking
cancer
central venous catheters
antiphospholipid syndrome
other inherited thrombophilias
Family history can be particularly informative. A family pattern of early, recurrent, or unexplained venous thrombosis may suggest that additional genetic or shared risk factors are present beyond rs6025 alone.
Relative risk is not the same as absolute risk
Relative risk compares the rate of an event between two groups. Absolute risk describes the actual probability that the event will occur over a particular period.
Suppose one group has a very low baseline risk. A several-fold relative increase may still result in a relatively low absolute annual probability for an otherwise healthy person. The situation can change when several risk factors occur together. Surgery, prolonged immobility, pregnancy, estrogen exposure, obesity, cancer, increasing age, and previous thrombosis can all increase baseline risk. For this reason, an rs6025 genotype cannot provide one universal blood-clot probability. Individual risk assessment requires medical and personal context that is not contained in a raw DNA file.
Factor V Leiden and estrogen-containing medication
Estrogen-containing contraceptives and some forms of hormone replacement therapy can independently increase venous thrombosis risk [R].
When estrogen exposure occurs in someone with Factor V Leiden, the combined risk may be greater than the effect of either factor considered separately.
The clinical relevance depends on factors such as:
whether one or two variant copies are present
whether the result has been clinically confirmed
personal history of thrombosis
family history
age
smoking
body weight
other medical conditions
the type and route of hormone treatment
A consumer DNA result should not be used by itself to start or stop contraception, hormone replacement therapy, aspirin, or anticoagulant medication. Anyone with a potentially significant finding should discuss medication decisions with an appropriate healthcare professional after clinical confirmation.
Factor V Leiden and pregnancy
Pregnancy and the postpartum period naturally increase clotting tendency [R]. This helps reduce bleeding during delivery but also increases susceptibility to venous thrombosis [R].
Factor V Leiden may increase that susceptibility further, especially when additional factors are present, such as:
a previous pregnancy-related clot
a strong family history
two variant copies
prolonged immobility
cesarean delivery
obesity
another thrombophilia
Factor V Leiden has also been studied in relation to miscarriage and other pregnancy complications [R]. Associations have been inconsistent, and the variant should not be presented as a direct explanation for pregnancy loss. Most women with Factor V Leiden have normal pregnancies.
Pregnancy-related prevention or treatment decisions must be individualized. The genotype alone does not determine whether anticoagulant medication is appropriate.
What raw DNA can show about Factor V Leiden
When rs6025 is present in a supported file, raw DNA analysis may show which genotype was recorded at that location.
This can provide useful genetic context, including:
whether the variant appears to be present
whether one or two copies were recorded
how the result relates to Factor V Leiden research
whether other supported clotting-related markers are present in the file
Raw DNA cannot determine:
whether a blood clot is currently present
whether someone will develop a clot
an exact personal-risk percentage
whether anticoagulant medication is needed
whether estrogen-containing medication is appropriate
whether all inherited thrombophilias are absent
whether acquired clotting disorders are present
current levels of coagulation proteins
the effect of every medical or environmental risk factor
Consumer genotyping also differs from clinical diagnostic testing. A potentially important raw DNA finding should be treated as a result that may warrant confirmation, not as a definitive medical diagnosis.
Why manual rs6025 interpretation can be difficult
Looking up one famous SNP may seem straightforward, but several problems can arise:
the marker may not be included in the file
the genotype may be recorded as a no-call
different sources may use opposite DNA strands
the variant may appear under several historical names
genotype letters may be mistaken for clinical transcript notation
a relative-risk estimate may be confused with personal absolute risk
one result may be interpreted without considering related findings
weak or outdated sources may be treated as equivalent to clinical databases
A raw DNA file can contain hundreds of thousands of rows. Researching each potentially relevant marker manually requires locating the correct rsID, verifying strand orientation, evaluating the strength of the evidence, and placing the result in context.
How GenesUnveiled analyzes Factor V Leiden rs6025
GenesUnveiled provides a structured way to analyze supported raw DNA files without manually searching through thousands of genetic markers. The platform can check whether rs6025 is present, match the recorded genotype to the expected forward-strand orientation, and display the finding within a consistent report format.
This helps reduce several common interpretation problems:
searching manually through a large text file
confusing C/T notation with G/A notation
overlooking missing variants or no-calls
treating an unverified allele direction as established
interpreting isolated SNPs without clear limitations
researching every marker separately across multiple databases
GenesUnveiled also organizes available results across categories such as:
High-Impact Variant Reports
health-risk reports
gene activity
pharmacogenetics
nutrition and metabolism
traits
GeneExplorer
Smart Summary
SNP Lookup
This broader structure is the main advantage over manually checking one allele at a time. A single public article can explain the general science of Factor V Leiden, while a structured analysis helps identify and organize the findings actually present in a user’s file.
You can begin with the free GeneExplorer, which includes F5, or view the available DNA reports and markers.
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