MTHFR: C677T

rs1801133 · Methylation & Folate Metabolism

The MTHFR C677T variant affects your body's ability to convert folic acid into its active form, methylfolate. This impacts methylation — a critical process for DNA repair, detoxification, and neurotransmitter production.

What This SNP Does

MTHFR (methylenetetrahydrofolate reductase) is an enzyme essential for the folate cycle. The C677T variant (Ala222Val) reduces enzyme activity. Heterozygous carriers have ~35% reduced function; homozygous individuals have ~70% reduced function. This can lead to elevated homocysteine levels, which is associated with cardiovascular risk and neural tube defects.

Genotype Meanings

Genotype	Status	What It Means
CC	Normal	Full enzyme activity. Standard folate metabolism.
CT	Carrier	~35% reduced enzyme activity. Consider methylfolate over folic acid. Monitor homocysteine.
TT	Homozygous	~70% reduced activity. Methylfolate supplementation recommended. Regular homocysteine monitoring important.

What You Can Do

If you carry one or two T alleles, consider switching from folic acid to methylfolate (5-MTHF). B12 (methylcobalamin) supports the methylation cycle. Get homocysteine levels tested — elevated levels may indicate inadequate methylation support.

This information is for educational purposes only and is not medical advice. Always consult a qualified healthcare provider before making health decisions based on genetic data. Genome Decoder does not diagnose, treat, or prevent any disease.