Factor V Leiden (rs6025) in your raw data
Factor V Leiden is one of the most clinically meaningful variants people find in their raw DNA — it affects blood clotting. That also makes it one to handle carefully: raw consumer data is a starting point, not a diagnosis. Here's what rs6025 is, how to find it in your 23andMe or AncestryDNA file, and what to do with the result.
This is educational information, not medical advice. Clotting risk is a clinical matter. If this variant appears in your data, or you or your family have a history of blood clots, talk to a healthcare professional about confirmatory testing.
What Factor V Leiden does
Factor V is a protein in your blood-clotting cascade. Normally, a regulator called activated protein C switches Factor V off when clotting should stop. The Factor V Leiden variant (rs6025, also written R506Q) changes Factor V so it resists being switched off — so clotting is harder to stop, raising the risk of abnormal clots.
The conditions it's associated with are venous thromboembolism (VTE) — mainly deep vein thrombosis (DVT) and pulmonary embolism (PE).
What the genotypes are associated with
| Genotype | Status | Associated risk |
|---|---|---|
| Two common alleles | Non-carrier | Baseline risk |
| One Leiden allele | Heterozygous | ~3–8x higher relative risk of venous clots |
| Two Leiden alleles | Homozygous | Substantially higher risk |
Two things keep this in perspective: relative risk isn't the same as absolute risk (most carriers never have a clot), and risk rises sharply with triggers — surgery, long immobility, estrogen-containing contraceptives, and pregnancy. That's exactly why knowing your status can be useful information to share with a doctor before, say, a major operation.
How to find rs6025 in your raw data
- Download your raw data (or from AncestryDNA / MyHeritage).
- Search it for
rs6025and read your genotype. - Or use our free DNA explorer — it reads your file in your browser, nothing uploaded.
Two important caveats for this marker specifically: strand orientation varies between files (so the exact letters differ), and consumer genotyping arrays can occasionally miscall a single position. For a variant with real medical weight, never treat the raw-data readout as final.
What to do with the result
If rs6025 flags as a carrier result — or if you have a personal or family history of clots regardless of what your file says — the right next step is a clinician and a confirmatory clinical test, not a self-assessment. Knowing your status is genuinely useful; acting on it is a job for your doctor.
For the rest of what your file contains, see our complete guide to analyzing 23andMe raw data, or browse the rest of the Quanome blog.
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Frequently asked questions
What is Factor V Leiden?
Factor V Leiden is a common inherited variant (rs6025, also called R506Q) in the F5 clotting gene. It makes Factor V resistant to being switched off, which tips the balance toward clotting and raises the risk of deep vein thrombosis and pulmonary embolism.
How do I find Factor V Leiden in my 23andMe raw data?
Search your raw DNA file for rs6025 and read the genotype. The Leiden (risk) allele is the less common one. Because strand orientation varies between files, and because consumer arrays can misread single markers, any result should be confirmed with clinical testing.
How much does Factor V Leiden raise clotting risk?
One copy (heterozygous) is associated with roughly a 3–8x higher risk of venous clots; two copies (homozygous) much higher. But most carriers never have a clot — absolute risk depends on age, surgery, immobility, hormones, pregnancy, and more.
Is a raw-data result a diagnosis?
No. Consumer raw data is not a clinical test. A single-marker readout can be wrong, and clotting risk is a medical matter. If rs6025 flags in your file, or you have a personal or family history of clots, see a clinician for confirmatory testing and advice.
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