MTHFR gene testing (C677T / A1298C genotype)

ND-recommended test reviewed: MTHFR gene testing (C677T/A1298C).
Indications reviewed: thrombophilia, cardiovascular risk, recurrent pregnancy loss evaluation; no validated indication for MTHFR genotyping identified.
Not ordered. Rationale discussed: professional genetics guideline concludes MTHFR status does not reliably predict these outcomes and should not be ordered for them. Ref: American College of Medical Genetics and Genomics 2013.
Patient informed test available privately via ND, or via direct-to-consumer genotyping. Patient given info page: https://labs.ajaxharwoodclinic.com/mthfr-genotype/patient
Revisit if: a specific, validated concern such as elevated homocysteine, folate deficiency, or a genuine thrombophilia indication arises, in which case test that marker directly.

Indicated when

None recorded.

Not indicated when

• —Ordering MTHFR C677T/A1298C genotyping as part of a routine evaluation for thrombophilia, recurrent pregnancy loss, or unexplained venous thromboembolism [1]
• —Ordering MTHFR genotyping to explain fatigue, mood symptoms, or general 'methylation' or detoxification concerns
• —Treating a direct-to-consumer (e.g. 23andMe) raw genotype report's MTHFR result as a clinically actionable finding

Why not

MTHFR polymorphism testing was historically ordered because reduced MTHFR enzyme activity was hypothesized to cause mild hyperhomocysteinemia, which was in turn hypothesized to raise the risk of venous thromboembolism, coronary heart disease, and recurrent pregnancy loss. The American College of Medical Genetics and Genomics' own practice guideline concludes that meta-analyses have since disproven the association between MTHFR polymorphism status and these outcomes, and that MTHFR testing 'should not be ordered as a part of a routine evaluation for thrombophilia' [1]. A Cochrane review similarly found no reduction in cardiovascular events from homocysteine-lowering interventions, undercutting the pathway MTHFR testing is meant to flag [2]. A positive MTHFR result in a patient without a validated indication does not change management, but commonly prompts unnecessary supplementation, anxiety about a 'genetic mutation,' and sometimes further unvalidated methylation-panel testing.

Better first step

If there is a concern about elevated homocysteine or folate status specifically, measure homocysteine and folate directly rather than inferring them from MTHFR genotype; a normal homocysteine makes the MTHFR genotype clinically irrelevant regardless of result. If thrombophilia is a genuine concern, use validated thrombophilia testing that does not include MTHFR.

Typical ND rationale

An ND may order or discuss MTHFR genotyping in a patient with fatigue, mood symptoms, migraines, recurrent pregnancy loss, or a family member with a known MTHFR variant, reasoning that this common genetic variant impairs the body's ability to process folate and methylate other compounds, and that identifying it explains symptoms and guides targeted supplementation, such as methylfolate instead of folic acid.

Ontario coverage & CONO orderability

OHIP status

unverified

MTHFR genotype testing does not appear by name in the 2026 Schedule of Benefits for Laboratory Services searched this session and does not appear on the CONO list, so billing status if a physician ordered it is unverified. Genetic testing performed by hospital genetics laboratories can have its specimen collected at a community lab under the Community Access Pilot's Category 1 provision, but this session found no evidence that any Ontario hospital genetics laboratory offers MTHFR polymorphism genotyping as a clinical service, consistent with the ACMG guideline against ordering it [4, 1]. Direct-to-consumer genotyping (e.g. 23andMe) is a separate, fully private-pay pathway regardless of physician or ND involvement. ND-ordered testing through any pathway is patient-paid regardless [5].

CONO orderable

No

Not on the CONO list under any name searched ('MTHFR', 'methylenetetrahydrofolate'). Not independently ND-orderable through the CONO pathway; patients most often obtain a result through direct-to-consumer genotyping services rather than a clinical laboratory order.

Linked conditions

• MTHFR mutation / methylation problems ↗

Counselling script

“MTHFR gene testing isn't something I'd order, because the research hasn't shown that this variant reliably predicts blood clots, pregnancy loss, or the other problems it was once thought to explain, and genetics experts now recommend against testing for it. If you're specifically worried about your homocysteine or folate level, I'd measure those directly instead, since a normal level makes the gene result irrelevant either way. If you already have an MTHFR result from a home DNA test, we don't need to act on it without a specific reason.”

Revisit if

• —Elevated homocysteine or folate deficiency is identified: manage directly
• —A genuine thrombophilia indication (e.g. unprovoked VTE, qualifying family or pregnancy-loss history) arises: use validated thrombophilia testing, not MTHFR

References

1. [1]American College of Medical Genetics and Genomics (ACMG) (2013). ACMG Practice Guideline: lack of evidence for MTHFR polymorphism testing. linkACMG: MTHFR testing has minimal clinical utility and should not be ordered as part of a routine thrombophilia evaluation
2. [2]Cochrane (2017). Homocysteine-lowering interventions for preventing cardiovascular events. linkNo reduction in cardiovascular events from homocysteine-lowering interventions compared with placebo
3. [3]Canadian Hematology Society / Choosing Wisely Canada (2022). Choosing Wisely Canada Labs Recommendations - Full List. linkCanadian Hematology Society/Choosing Wisely Canada: don't order thrombophilia testing in women with early pregnancy loss
4. [4]Ontario Ministry of Health (2026). INFOBulletin 260503: 2026-2027 Community Access Pilot for Laboratory Services. linkCommunity Access Pilot Category 1 covers specimen collection for hospital-lab genetic tests; no evidence MTHFR genotyping is offered as a clinical service
5. [5]Ontario Ministry of Health (2026). Ontario Health Insurance Plan: Schedule of Benefits for Laboratory Services (effective April 1, 2026). linkTests ordered by anyone other than an authorized provider, including NDs, are not insured services