MTHFR Genotype Test

The MTHFR genotype refers to inherited changes in a gene that produces an enzyme called methylenetetrahydrofolate reductase (MTHFR). This enzyme plays a key role in a vital process called one-carbon metabolism, which supports DNA repair and methylation—mechanisms that are essential for healthy cell function. More specifically, MTHFR helps convert folate (vitamin B9) into its active form and keeps levels of homocysteine—a potentially harmful amino acid—under control.

We each inherit two copies of the MTHFR gene, one from each parent. The most studied variants are called C677T and A1298C. People with two copies of the C677T variant (homozygous TT genotype) have only about 30% of normal enzyme activity. Those with one C677T and one A1298C variant (compound heterozygotes) also have reduced function. This can lead to higher levels of homocysteine in the blood, especially in people with low folate intake.

Elevated homocysteine—known as hyperhomocysteinemia—is associated with a higher risk of cardiovascular disease, blood clots, cognitive decline, and certain pregnancy complications. However, having an MTHFR mutation does not automatically mean you have high homocysteine or are at high risk. In countries like the United States, where food is fortified with folic acid, many people with MTHFR mutations maintain normal homocysteine levels.

While MTHFR variants have been studied in connection with psychiatric disorders, Alzheimer’s disease, infertility, and miscarriage, the science is still evolving. Many of these associations are weak, inconsistent, or dependent on other genetic and environmental factors. For example, while some studies suggest a link between MTHFR and depression or autism, others show no significant association.

If you do carry MTHFR variants, the most practical action is to ensure you get enough folate from food or supplements. Folate-rich foods include leafy greens, beans, citrus fruits, and fortified grains. For women planning pregnancy, taking a daily prenatal vitamin with at least 0.4 mg (400 mcg) of folic acid is universally recommended to reduce the risk of neural tube defects in babies—regardless of MTHFR status.