evidence: The abbreviation MTHFR refers to a relatively common genetic mutation. It stands for methylenetetrahydrofolate reductase, and having this mutation may lead to high levels of homocysteine in the blood and low levels of folate and other vitamins. [...] Conditions that may be associated with MTHFR include: [...] A person with two gene variants or who is homozygous for the MTHFR mutation may have an increased chance of health conditions.