rs1799963
Prothrombin G20210A
What this position does
A change in the prothrombin gene that raises circulating prothrombin and, with it, clotting tendency. The second most common inherited clotting variant after Factor V Leiden.
What each result means
| If you carry | What it means |
|---|---|
| No copies of the effect version GG | You do not carry this variant Neither copy carries this variant. |
| One copy AG | You carry one copy, so clotting risk is modestly raised in specific situations Roughly two to three times the background risk of venous clots, from a low base. The same situational advice applies as for Factor V Leiden. |
| Two copies AA | You carry two copies, worth raising with a doctor Uncommon, and a higher risk again. Worth a clinical confirmation and a conversation with a doctor. |
How common each version is
| Ancestry group | A (the effect version) | |
|---|---|---|
| African | 0.0% | |
| American | 1.4% | |
| East Asian | 0.0% | |
| European | 0.8% | |
| South Asian | 0.0% |
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 | GG | AG | AA |
|---|---|---|---|
| African | 661 / 661 | 0 / 661 | 0 / 661 |
| European | 495 / 503 | 8 / 503 | 0 / 503 |
| East Asian | 504 / 504 | 0 / 504 | 0 / 504 |
| South Asian | 489 / 489 | 0 / 489 | 0 / 489 |
| American | 338 / 347 | 8 / 347 | 1 / 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 rs1799963?
rs1799963 is a position in the F2 gene on chromosome 11. A change in the prothrombin gene that raises circulating prothrombin and, with it, clotting tendency. The second most common inherited clotting variant after Factor V Leiden.
What does it mean if I have AA at rs1799963?
You carry two copies, worth raising with a doctor. Uncommon, and a higher risk again. Worth a clinical confirmation and a conversation with a doctor.
What does it mean if I have GG at rs1799963?
You do not carry this variant. Neither copy carries this variant.
How do I find out my rs1799963 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.