rs602662
Vitamin B12 levels
What this position does
The same FUT2 gene behind secretor status also shows up as the strongest common genetic influence on measured vitamin B12 in blood, probably through its effect on which bacteria live in the gut and on H. pylori infection.
What each result means
| If you carry | What it means |
|---|---|
| No copies of the effect version GG | You do not carry the higher-level version Neither copy carries the higher-B12 version. |
| One copy AG | One copy, so modestly higher B12 on a blood test Associated with modestly higher measured B12. |
| Two copies AA | Two copies, so the highest average B12 on a blood test Associated with the highest average measured B12. Note the direction: this shifts the number your blood test reports, which can make interpretation of a borderline result tricky. |
How common each version is
| Ancestry group | A (the effect version) | |
|---|---|---|
| African | 49.2% | |
| American | 35.2% | |
| East Asian | 0.4% | |
| European | 46.8% | |
| South Asian | 28.3% |
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 | 171 / 661 | 329 / 661 | 161 / 661 |
| European | 147 / 503 | 241 / 503 | 115 / 503 |
| East Asian | 500 / 504 | 4 / 504 | 0 / 504 |
| South Asian | 262 / 489 | 177 / 489 | 50 / 489 |
| American | 157 / 347 | 136 / 347 | 54 / 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.
Related
- rs601338 — Secretor status
Where this fits
Common questions
What is rs602662?
rs602662 is a position in the FUT2 gene on chromosome 19. The same FUT2 gene behind secretor status also shows up as the strongest common genetic influence on measured vitamin B12 in blood, probably through its effect on which bacteria live in the gut and on H. pylori infection.
What does it mean if I have AA at rs602662?
Two copies, so the highest average B12 on a blood test. Associated with the highest average measured B12. Note the direction: this shifts the number your blood test reports, which can make interpretation of a borderline result tricky.
What does it mean if I have GG at rs602662?
You do not carry the higher-level version. Neither copy carries the higher-B12 version.
How do I find out my rs602662 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.