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

MTR and MTRR sit right next to MTHFR on most methylation reports, and they’re often glossed over or lumped in with a wave of worry about “bad methylation.” This guide gives them a fair, plain-English treatment: what they do, how they connect to vitamin B12 and homocysteine, and what the evidence genuinely supports.

What MTR and MTRR do

These two genes work as a pair in the same step of the methylation cycle:

• MTR codes for an enzyme (methionine synthase) that helps recycle the amino acid homocysteine back into methionine — a key recycling step. It relies on vitamin B12 to do this.
• MTRR codes for a helper enzyme that keeps MTR’s B12 working properly, effectively “reactivating” it so the MTR step can keep running.

Think of MTR as the worker and MTRR as the maintenance crew that keeps the worker’s B12 tool functioning. Both are part of how your body manages homocysteine, alongside MTHFR.

The common variants

The variants you’ll typically see on a report include MTR (rs1805087, sometimes written A2756G) and MTRR (rs1801394, or A66G). As with all these markers, you can carry no copies, one, or two — and these variants are common in the general population.

What the research actually shows

MTR and MTRR variants have been studied mainly for associations with homocysteine levels and vitamin B12 metabolism. As with MTHFR, the findings are relative and often modest — some studies find small associations, sometimes only when combined with other variants or with low B12 intake, and results vary between populations.

The honest takeaway: carrying these variants is common and, on its own, tells you very little definitive about your health. They may nudge how efficiently the B12-dependent recycling step runs — they don’t determine your homocysteine, your B12 status, or any diagnosis.

How to find your result

Your existing 23andMe or AncestryDNA file already contains these markers (look up rs1805087 for MTR and rs1801394 for MTRR). Raw files can report variants on a different strand than research papers use, which makes manual reading error-prone; an analysis tool reports your genotype directly and handles the strand for you.

What your result means — and what to do

If you carry one or more MTR/MTRR variants:

• They’re common and, alone, not a diagnosis.
• Any associations relate to B12-dependent homocysteine recycling and are population-level, not personal predictions.
• If B12 or homocysteine is a real question for you, the useful steps are actual blood tests and a qualified practitioner’s input — not acting on a gene result by itself. We don’t give supplement or dosing advice here, because that belongs with someone who can see your labs.

See your own result

Curious what you carry? Your existing raw file already contains the MTR and MTRR markers — no new test needed.

Upload your 23andMe or AncestryDNA file to see your MTR and MTRR results in a plain-language variant report, and interpret them with your practitioner and your actual bloodwork.

---

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.

Read Russell’s Full Professional Profile & Clinical Credentials
View Published Genetic Health Literature & Books