They are at least 13 different known genetic polymorphisms involving in MTHFR gene. Depending on what mutation or combination of mutations you have and whether you are heterozygous or homozygous for the the defect, you will either be unable to transform folate or synthetic folic acid to the active form, L Methylfolate, or have limited ability to make L Methylfolate. L Methylfolate is required to produce the precursor BHT that produces seritonin, dopamine, and norepinephrine. Go to MTHFR Mutation | MTHFR Gene Mutation | What is MTHFR? - MTHFR.net to find out all about it. You can also have your blood tested for MTHFR mutations for $195 at MTHFR Genotyping Laboratory Genetic Test | Seeking Health