“What is the MTHFR Mutation? MTHFR (or methylenetetrahydofolate reductase) is an enzyme required to convert folate to methionine, which is then used in the production of necessary amino acids and other compounds. When MTHFR genes are mutated, then MTHFR is not produced well, homocysteine (thought to be involved in atherosclerosis and other health issues) builds up and essential proteins are not made. There are at least 40 different MTHFR mutations known, but the two that occur at positions C677T or A1298C are most problematic. These occur in over 30% of individuals, but seem to be more common in PWCS , in my experience. The “treatment” is to take methyl-folate and methyl-cobalamin (B12), which is recommended for most PWCs anyway, so it is not necessary to take the blood test for these mutations. I generally recommend 400 to 1000 mcg of methyl-folate daily, and 1000 to 5000 mcg of methyl-B12, both of which are available over-the-counter. The test for MTHFR mutations is frequently covered by insurance, but as of this writing (November 2014) Medicare is considering disallowing it.”