AncestryDNA MTHFR C677T marker
MTHFR rs1801133 in AncestryDNA raw data.
If you are searching an AncestryDNA raw DNA file for MTHFR C677T, the marker most people mean is rs1801133. GenoSight can help you check whether that marker is present, then keep interpretation cautious inside a broader educational Detox & Methylation report.
Start with marker coverage
Do this before interpreting the raw letters.
- Use the downloaded AncestryDNA raw DNA file, usually named dna-data-(date).zip
- Search for rs1801133 in the text file or use a browser-only local marker checker
- Treat missing rs1801133 as a coverage issue, not a clinical result
- Interpret C677T with A1298C, COMT, folate context, labs, symptoms, and clinician guidance
What to know before you search the file.
A raw-data search can answer a narrow coverage question. It cannot tell you, by itself, whether you have a methylation issue or need a supplement.
AncestryDNA raw data is uninterpreted
Ancestry describes downloadable DNA data as uninterpreted raw data generated from an AncestryDNA test and used for ancestry, matching, and traits.
Ancestry reports forward-strand genotypes
Ancestry states that SNP genotypes in downloaded DNA data are reported on the genomic forward strand with respect to GRCh37.
GenoSight keeps the next step cautious
The local checker shows marker presence and raw genotype strings. A full report adds context without turning one SNP into supplement instructions.
Keep raw data inside its limits.
GenoSight is educational only. It can help you move from a raw marker lookup to a structured report, but medical decisions require clinical confirmation, labs, and a qualified professional.
Ancestry support: downloading DNA data
Explains raw-data downloads, .txt format, dna-data-(date).zip files, email link timing, forward-strand GRCh37 reporting, and security caveats.
Ancestry account-data download
Explains confirming DNA-data downloads, download-link expiration, managed-test access, and privacy considerations after download.
MedlinePlus MTHFR gene
Describes MTHFR and notes that C677T and 1298A>C are common studied polymorphisms while keeping medical context separate.
Next steps with a AncestryDNA file
Check rs1801133 locally
Use the browser-only checker to see whether the marker appears in your file without uploading it.
ContinueCompare rs1801131
Read the A1298C marker page so C677T is not interpreted in isolation.
ContinueRun Detox & Methylation
Use free signup credits or choose monthly to generate a broader educational report from a compatible raw file.
Continuers1801133 and AncestryDNA questions
Can I find rs1801133 in AncestryDNA raw DNA data?
Sometimes. AncestryDNA download format, lab pipeline, and no-call results can vary, so the right first step is checking whether your specific downloaded file contains rs1801133.
What does rs1801133 mean in MTHFR?
rs1801133 is commonly discussed as MTHFR C677T. A raw genotype is not a methylation test, diagnosis, or supplement instruction, and it should be interpreted with A1298C, COMT, folate context, labs, symptoms, and clinician guidance.
Why do my AncestryDNA MTHFR letters not match C/T examples?
Consumer raw files, SNPedia-style pages, and blog posts can use different strand conventions. C pairs with G and T pairs with A, so a raw rs1801133 call such as G/G may be the complement of a C/C-style example, and A/G may line up with C/T-style notation. For rs1801131, T/G can similarly appear where another source discusses A/C. GenoSight keeps marker detection, strand caveats, and interpretation separate so raw letters do not turn into overconfident health advice.
What if my AncestryDNA file does not show rs1801133?
That usually means the marker is missing, uncalled, or represented differently in that file. It does not prove anything clinically by itself.
Can GenoSight analyze my AncestryDNA file for MTHFR?
Yes, if it is a compatible AncestryDNA raw genotype file. GenoSight can run an educational Detox & Methylation report that frames MTHFR with COMT, folate context, caveats, and source notes.