Introduction to MTHFR and methylation
MTHFR stands for methylene-tetrahydrofolate reductase.
It is an enzyme that converts folate you eat into the active form (5-Methyltetrahydrofolate).
You can see from the pathway below that the folate you eat (DHF – dihyrofolate) has to be converted via many steps to the active folate 5-MTHFR.
The MTHFR enzyme affects this at the last step. So if you have a mutation in the gene then its going to be affecting how much active folate you have available.
Source: MTHFR Support Australia