Markers / Condition
Which genes affect iron, B12 and folate?
Nutrient handling is where consumer genetics is at its most oversold. One variant here is genuinely worth knowing about, because iron overload is common, silent for decades and completely treatable if caught. The folate genes beside it are the most over-interpreted positions in the whole field.
The markers
| Marker | Gene | What it does | Evidence |
|---|---|---|---|
| rs1800562 | HFE | Iron overload, C282Y | established |
| rs1799945 | HFE | Iron overload, H63D | established |
| rs602662 | FUT2 | Vitamin B12 levels | strong |
| rs601338 | FUT2 | Secretor status | established |
| rs1801133 | MTHFR | MTHFR C677T, and why it is oversold | established |
| rs1801131 | MTHFR | MTHFR A1298C | established |
| rs1801394 | MTRR | The other folate gene, MTRR | moderate |
Iron overload, C282Y
rs1800562 · HFE
Hereditary haemochromatosis makes the gut absorb more iron than the body can dispose of, and it accumulates in the liver, heart and pancreas over decades. It is one of the most common inherited conditions in people of northern European descent, and one of the most treatable if it is found early.
Two copies: You carry two copies, which is worth a simple blood test
Iron overload, H63D
rs1799945 · HFE
The second and much milder HFE variant. On its own it causes very little; paired with C282Y it occasionally produces mild iron loading.
Two copies: You carry two copies, which rarely causes iron problems by itself
Vitamin B12 levels
rs602662 · FUT2
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.
Two copies: Two copies, so the highest average B12 on a blood test
Secretor status
rs601338 · FUT2
FUT2 decides whether you put blood-group sugars into saliva, gut lining and other secretions. About a fifth of Europeans have two broken copies and are non-secretors, which changes which gut bacteria settle in and which stomach bugs can get a grip.
Two copies: Non-secretor
MTHFR C677T, and why it is oversold
rs1801133 · MTHFR
This is the single most over-interpreted position in consumer genetics. It genuinely does reduce the activity of an enzyme in folate metabolism. What it does not do is most of what the internet says it does.
Two copies: You carry two copies, which is common and still changes little
MTHFR A1298C
rs1801131 · MTHFR
The second common MTHFR variant, usually reported alongside C677T. It reduces enzyme activity less than C677T does.
Two copies: You carry two copies, which still changes very little
The other folate gene, MTRR
rs1801394 · MTRR
MTRR keeps the enzyme that recycles homocysteine back into methionine running, using vitamin B12. It is usually reported next to MTHFR, and it attracts some of the same overreach.
Two copies: You carry two variant copies
Which versions do you carry?
All of these are readable from an ordinary home DNA test file, in your browser, without uploading it anywhere.
Read my fileCommon questions
Which genes affect iron, B12 and folate?
Nutrient handling is where consumer genetics is at its most oversold. One variant here is genuinely worth knowing about, because iron overload is common, silent for decades and completely treatable if caught. The folate genes beside it are the most over-interpreted positions in the whole field. The markers most often cited are rs1800562 in HFE, rs1799945 in HFE, rs602662 in FUT2, rs601338 in FUT2, rs1801133 in MTHFR.
What does rs1800562 do?
Hereditary haemochromatosis makes the gut absorb more iron than the body can dispose of, and it accumulates in the liver, heart and pancreas over decades. It is one of the most common inherited conditions in people of northern European descent, and one of the most treatable if it is found early. Carrying two copies: you carry two copies, which is worth a simple blood test.
What does rs1799945 do?
The second and much milder HFE variant. On its own it causes very little; paired with C282Y it occasionally produces mild iron loading. Carrying two copies: you carry two copies, which rarely causes iron problems by itself.
What does rs602662 do?
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. Carrying two copies: two copies, so the highest average b12 on a blood test.
What does rs601338 do?
FUT2 decides whether you put blood-group sugars into saliva, gut lining and other secretions. About a fifth of Europeans have two broken copies and are non-secretors, which changes which gut bacteria settle in and which stomach bugs can get a grip. Carrying two copies: non-secretor.
Reference information, not medical advice and not a diagnosis. See the medical disclaimer.