CYP2R1: the vitamin-D activation gene
Two genes can leave you short on vitamin D. This one runs the switch that turns it on.
Vitamin D doesn't do much until your body activates it, and your liver handles the first step. CYP2R1 makes the enzyme that does that conversion. One common version of the gene, rs10741657, shows up again and again in people who run low on vitamin D and tip into deficiency more often.
What CYP2R1 does
Like the GC variant, the honest read is this: your genes nudge your starting point lower, not how well you respond to a supplement. So the play is the same either way. Get your level checked, and if you're short, take D3 with K2.
Carry this one and the GC variant together and the odds of running low add up. That's a good reason to actually measure a 25(OH)D level instead of guessing.
Your variants, decoded
The C allele tracks with lower 25(OH)D and a higher shot at deficiency.
| AA | Typical vitamin-D activation. |
| AC | One copy. Levels tend to run a bit lower. |
| CC | Two copies. Lowest of the three, and the genotype where a blood test earns its keep most. |
Genotypes are shown order-insensitively and on the forward strand; your own export may print the complementary letters — the meaning is the same.
What the research suggests
Your CYP2R1 rs10741657 C allele tracks with lower circulating vitamin D and a higher chance of running deficient, so it's worth testing your level and thinking about D3. One thing to be clear on: the vitamin-D benefit is GENERAL, the same for anyone. It's not unique to your genotype. Your genes raise the odds you're starting low, not how you respond to the supplement.
PubMed 30120973 · CYP2R1 rs10741657 & 25(OH)D / deficiency risk
Educational only — not medical advice. “General evidence” means the finding is real but the supplement’s benefit isn’t unique to your genotype.
See this matched to your own DNA — free.
Upload your 23andMe or AncestryDNA file and get your actual CYP2R1 result, plus every other actionable variant — each line cited, your file never stored.
Questions
What does CYP2R1 do for vitamin D?
It runs the first step that turns vitamin D into the form your body can use. One common version of the gene tracks with lower blood levels and a higher chance of deficiency.