By Russell Browne (Dip. Adv. Nut.) · Specialist in Genetic Nutrition & Methylation Protocols

Here’s a fact that surprises a lot of people: your 23andMe file almost certainly already contains your MTHFR result. The company just doesn’t surface it in its standard reports. This guide shows you the two markers to look for, how to read them without falling into the most common trap, and why a tool usually beats doing it by hand.

The two markers you’re looking for

MTHFR has two commonly studied variants, and each has a genetic ID (an “rs number”) you can search for in your raw data:

• C677T → rs1801133
• A1298C → rs1801131

Both are typically included on the genotyping used by 23andMe and AncestryDNA, so they should be present in your downloaded file.

Option A: Check it by hand

If you want to read the file directly:

1. Download your raw data and unzip it to get the text file. (See our download guide if you haven’t.)
2. Open the file, or use your platform’s “browse raw data” search box, and search for rs1801133 (and then rs1801131).
3. You’ll see the marker and the two letters you carry at that position.

The trap: the strand flip

Here’s what trips almost everyone up. Raw data files often report these positions on the opposite DNA strand from research papers. So for C677T, where a study says C (typical) and T (variant), your file may show G and A instead. They mean the same thing:

• G in your file = C (typical)
• A in your file = T (variant)

So a raw-data readout of “GG” corresponds to no C677T variant, “GA” to one copy, and “AA” to two copies. If you skip this step, it’s easy to misread your own result — which is exactly why manual checking causes so much confusion.

Option B: Let a tool do it (usually easier)

An analysis tool takes your uploaded file, resolves the strand issue automatically, and reports your genotype for both MTHFR variants in plain language — no rs-number hunting, no strand math. For most people this is faster and less error-prone than reading the text file directly, and it surfaces other variants in the same pass.

Reading your result sensibly

Once you have your genotype for C677T and A1298C:

• Remember these variants are common, and a result is not a diagnosis.
• They’re associated with relative shifts in things like folate processing and homocysteine — not certainties about your health.
• What, if anything, to do about your result depends on your full clinical picture and belongs with a qualified practitioner. This guide is about finding and reading your result, not treating it.

See your result the easy way

Skip the strand math. Your existing file already contains rs1801133 and rs1801131.

Upload your 23andMe or AncestryDNA file to see your MTHFR result — both variants, correctly interpreted — in a plain-language variant report you can take to your practitioner.

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About the Author

Russell Browne (Dip. Adv. Nut.)
Specialist in Genetic Nutrition & Methylation Protocols

Russell Browne is a qualified practitioner of Advanced Nutrition, Advanced Herbalism, and Homeopathy, with a specialized clinical focus on genetic nutrition, methylation pathways, and detoxification. With years of dedicated clinical experience helping patients decode complex chronic health issues, Russell is also the author of How to Treat Your MTHFR Gene Mutations the Right Way – The Genetic Advantage and several works on genetic wellness. He is committed to bridging the gap between complex genetic data and practical, root-cause clinical care.

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