rs6025
Factor V Leiden
What this position does
A change in clotting factor V that makes it resist being switched off, so clots form a little too readily. It is carried by roughly one in twenty people of European descent.
What each result means
| If you carry | What it means |
|---|---|
| No copies of the effect version CC | You do not carry Factor V Leiden Neither copy carries Factor V Leiden. |
| One copy CT | You carry one copy, so clotting risk is raised in specific situations Raises the lifetime risk of deep vein thrombosis several-fold from a low base. The practical significance is situational: long-haul flights, surgery, pregnancy and combined oral contraceptives all add to it, and that last one is worth raising with a doctor. |
| Two copies TT | You carry two copies, a higher clotting risk worth raising with a doctor A substantially higher clotting risk than one copy. Worth confirming with a clinical test and discussing with a doctor, particularly before surgery or pregnancy. |
Worth knowing. Most carriers never have a clot. This changes what you do in high-risk situations; it does not change everyday life.
How common each version is
| Ancestry group | T (the effect version) | |
|---|---|---|
| African | 0.0% | |
| American | 1.0% | |
| East Asian | 0.0% | |
| European | 1.2% | |
| South Asian | 1.1% |
1000 Genomes Project phase 3, via Ensembl, retrieved 2026-09-23. These groupings are coarse and flatten a great deal of internal diversity, particularly within Africa. A variant being common somewhere tells you where a piece of your ancestry probably comes from, and nothing else.
How many people carry each result
| Ancestry group | CC | CT | TT |
|---|---|---|---|
| African | 661 / 661 | 0 / 661 | 0 / 661 |
| European | 492 / 503 | 10 / 503 | 1 / 503 |
| East Asian | 504 / 504 | 0 / 504 | 0 / 504 |
| South Asian | 478 / 489 | 11 / 489 | 0 / 489 |
| American | 340 / 347 | 7 / 347 | 0 / 347 |
Counts of people, not modelled frequencies: every one of the 2,504 individuals sequenced by the 1000 Genomes Project phase 3, tallied by the genotype they carry. Deriving these from allele frequencies instead would assume random mating inside each group and undercount the homozygotes.
How to find out which you have
If you have taken a test with 23andMe, AncestryDNA, MyHeritage, Family Tree DNA, TellMeGen or Living DNA, this position is very likely already in the raw data file they gave you. You do not need another test.
One thing to watch if you look it up by hand: testing companies report some positions from one DNA strand and some from the other, and the file does not say which. Read the letters as they appear and you will get the opposite of the truth for some positions. Sequencings resolves that automatically.
Source
Coordinates and allele pair verified against Ensembl GRCh37. Direction of effect verified against VEP protein consequences or 1000 Genomes population frequency. Category: Health-adjacent.
Where this fits
Common questions
What is rs6025?
rs6025 is a position in the F5 gene on chromosome 1. A change in clotting factor V that makes it resist being switched off, so clots form a little too readily. It is carried by roughly one in twenty people of European descent.
What does it mean if I have TT at rs6025?
You carry two copies, a higher clotting risk worth raising with a doctor. A substantially higher clotting risk than one copy. Worth confirming with a clinical test and discussing with a doctor, particularly before surgery or pregnancy.
What does it mean if I have CC at rs6025?
You do not carry Factor V Leiden. Neither copy carries Factor V Leiden.
How do I find out my rs6025 genotype?
If you have taken a home DNA test, this position is very likely in the raw data file you were given. Sequencings reads that file in your browser without uploading it, and resolves which DNA strand each position was reported from, which is the step most manual lookups get wrong.
This is reference information, not medical advice, and not a diagnosis. See the medical disclaimer. Category: Health-adjacent.