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CardiovascularEvidence 1B
rs1801133 · MTHFR
Risk allele: T
Risk-Allele Phenotype
C677T variant reduces enzyme activity to ~65%; associated with elevated plasma homocysteine and increased cardiovascular thrombosis risk, especially in folate-deficient states.
Reference-Allele Phenotype
Normal MTHFR enzyme activity and homocysteine metabolism with adequate folate status.
Evidence Level
1B — Strong — single high-quality study See methodology for how we grade evidence.
Cross-References
Informational only
This page summarizes population-level evidence about a genetic variant. It is not a diagnosis. Your individual risk depends on your full genome, lifestyle, environment, and family history. Consult a healthcare provider for personalized medical advice.
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