How to Find Your MTHFR Status in 23andMe Raw Data

23andMe stopped reporting MTHFR results directly in their consumer reports years ago, but the underlying raw genotype data is still included in every test. This guide walks through exactly how to find your MTHFR C677T and A1298C status using your existing 23andMe or AncestryDNA raw data file — no additional testing required.

Step 1: Download your raw DNA data

From 23andMe: Log in on a desktop browser (not the mobile app — raw data download is not available on mobile). Click your profile icon → Settings → scroll to "23andMe Data" → click "Access Your Data" → click "Download Raw Data". You'll receive an email with the download link.

From AncestryDNA: Log in on desktop → Settings → "Download DNA Data" → confirm via email → wait for the file (can take 24 hours) → download from the email link.

The file you download is a compressed .zip containing a .txt file. For most uses, including the lookup below, you need to unzip it first. The unzipped .txt file is what we'll be searching.

Step 2: Know what to search for

MTHFR has two clinically relevant variants, each identified by a unique rs (reference SNP) identifier:

MTHFR C677T = rs1801133 — the catalytic variant that directly impairs folate conversion.

MTHFR A1298C = rs1801131 — the regulatory variant that affects BH4 production and neurotransmitter synthesis.

Both are tested by every consumer genetics platform that uses standard SNP arrays (23andMe v3, v4, v5; AncestryDNA all generations; MyHeritage; Living DNA).

Step 3: Open the file and search

The raw data .txt file is plain text. Each line contains one SNP with the format: rs ID, chromosome, position, genotype. Open the file in any text editor — Notepad on Windows, TextEdit on Mac, or any code editor.

Use Ctrl+F (Windows) or Cmd+F (Mac) to search for rs1801133. You'll see one line containing this rs ID. The last column (after the position number) is your genotype. It will be a two-letter code like CC, CT, or TT.

Then search for rs1801131 the same way. Read the genotype in the last column.

Step 4: Interpret your results

For rs1801133 (C677T): CC = normal/reference, no impairment. CT = heterozygous, approximately 35% reduced enzyme activity. TT = homozygous, approximately 70% reduced enzyme activity.

For rs1801131 (A1298C): AA = normal/reference. AC = heterozygous. CC = homozygous. Note: this variant uses A/C rather than C/T because the SNP is on the opposite DNA strand to how A1298C is conventionally written. The biology is the same — what matters is whether you have zero, one, or two variant copies.

If you carry one copy of C677T and one copy of A1298C (CT for rs1801133 and AC for rs1801131), you are compound heterozygous — which is functionally different from being homozygous for either variant alone, and explained in detail in our heterozygous vs homozygous guide.

What this does and doesn't tell you

Knowing your MTHFR status is a starting point, not an endpoint. The variant tells you about enzyme activity. It does not tell you about your homocysteine level, your folate intake, your riboflavin status, or — critically — your COMT genotype, which determines how you'll respond to methylation supplementation.

For a complete methylation picture, the relevant variants extend beyond MTHFR to include COMT (rs4680), MTR (rs1805087), MTRR (rs1801394), CBS (rs234706), MAOA, and the broader B-vitamin pathway genes. Knowing MTHFR alone is useful but incomplete.

What to do next

If you have an elevated homocysteine measurement and TT or compound heterozygous MTHFR status, a methylation-focused intervention is reasonable to consider with a qualified clinician. If your homocysteine is normal despite a TT genotype, aggressive supplementation is unlikely to add value.

For a full personalised analysis that integrates MTHFR with the surrounding variant network and translates it into a specific protocol, that's what Genova Lab does — take your raw data, read it variant by variant, and build a protocol around your actual genome rather than a textbook average.

This article is for educational purposes only. It is not medical advice, a diagnosis, or a substitute for clinical assessment. Any supplementation protocol should be considered in the context of your individual health history and, where appropriate, in consultation with a qualified clinician.