MTHFR C677T raw DNA marker
MTHFR C677T rs1801133 in raw DNA data.
If you are searching your raw DNA file for MTHFR, rs1801133 is usually the C677T marker people mean. GenoSight can check marker coverage locally, then place the result inside a cautious educational methylation report.
Marker-first workflow
Check coverage before you interpret anything.
- Browser-only local marker check
- Raw genotype string only
- No methylfolate recommendation on the free page
- Full report adds folate and B-vitamin context
The raw marker is the beginning, not the answer.
C677T can be meaningful context, but it is easy to overstate. A useful report keeps the raw call, missing coverage, strand caveats, and health context separate.
What rs1801133 is
rs1801133 is the common MTHFR C677T marker many people search for after opening a 23andMe, AncestryDNA, or MyHeritage raw genotype file.
What it is not
A raw rs1801133 genotype is not a methylation-level test, diagnosis, or supplement instruction. It is one inherited marker that needs context.
How GenoSight handles it
GenoSight checks whether the marker is present, then frames MTHFR alongside A1298C, COMT, B-vitamin context, goals, symptoms, and clinician boundaries.
Evidence boundary
MTHFR C677T is a well-known folate-pathway variant, but consumer raw DNA is still educational context. Clinically meaningful decisions belong with appropriate labs and a qualified clinician.
Check C677T in your provider file.
The exact next step depends on which raw DNA export you have. Each provider guide keeps marker coverage, file format, and clinical boundaries separate.
MTHFR C677T rs1801133 questions
Can I find MTHFR C677T rs1801133 in my 23andMe raw data?
Often, yes, but coverage varies by provider and chip version. Use the browser-only MTHFR and COMT checker to see whether rs1801133 is present in your specific raw file.
Why might my file show A/G instead of C/T?
Consumer raw files and public databases can represent variants on different DNA strands. That is why GenoSight separates marker detection from interpretation and avoids overclaiming from raw letters alone.
Does MTHFR C677T mean I need methylfolate?
Not automatically. Supplement decisions depend on labs, diet, pregnancy status, symptoms, medications, and clinician guidance. GenoSight reports are educational, not prescribing advice.
Which GenoSight report should I start with?
For MTHFR C677T questions, Detox & Methylation is the most direct first report. It currently fits inside the 250-credit no-card signup grant.