MTHFR C677T
One copy of the MTHFR C677T variant detected.
You have one copy of the MTHFR C677T DNA change.
A common variant that modestly reduces the activity of an enzyme involved in folate metabolism. The clinical significance for healthy adults with adequate folate intake is minimal.
This is a common DNA change that slightly lowers the activity of an enzyme that processes folate. If you eat normally, the real-world impact is minimal.
What this means
MTHFR converts folate into its active form, which the body needs to recycle homocysteine. The C677T variant lowers enzyme activity. Two copies modestly raise plasma homocysteine, which has been linked to subtle increases in cardiovascular and neural tube defect risk, but high-quality trials of homocysteine-lowering therapy have not improved outcomes. Routine testing is *not* recommended by clinical genetics societies. We include it here because patients ask about it, not because it should drive decisions.
The MTHFR gene makes an enzyme that turns folate (vitamin B9) into the active form your body uses, including for recycling a chemical called homocysteine. This DNA change lowers the enzyme's activity. Two copies modestly raise homocysteine levels in your blood, which has been loosely linked to small increases in heart disease and birth defect risk — but good-quality trials of lowering homocysteine haven't improved outcomes. The main medical genetics organisations specifically recommend against testing for this routinely. We include it because so many people ask, not because it should change anything you do.
Caveats
- The American College of Medical Genetics explicitly recommends against routine MTHFR testing as a clinical investigation.
- Population-level supplementation of folic acid largely neutralises the variant's metabolic impact.
- Claims that this variant causes a wide range of symptoms (fatigue, depression, miscarriage) are not supported by good-quality evidence.