Methylenetetrahydrofolate reductase (MTHFR) is an enzyme that breaks down the amino acid homocysteine. If the MTHFR gene that codes for this enzyme mutates, it may contribute to a variety of health conditions ranging from depression to some cancers.

People have two MTHFR genes, inheriting one from each of their parents. Mutations can affect one (heterozygous) or both (homozygous) of these genes.

There are two common types, or variants, of MTHFR mutations: C677T and A1298C. These gene mutations are relatively common. Around 47%Trusted Source of people of Hispanic descent and 36% of Europeans are carriers for the C677T variant.

The mutations can lead to high levels of homocysteine in the blood, which may contribute to health conditions, including birth anomalies and coronary heart disease.

This article looks at MTHFR mutations in more detail, including related health conditions, diagnosis, and treatment options. It also discusses how MTHFR mutations can affect pregnancy.

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Mutations in the MTHFR gene can affect the body’s ability to process amino acids — namely, homocysteine — which can lead to some adverse health outcomes.

ResearchTrusted Source associates the following conditions with MTHFR gene variants:

  • Hyperhomocysteinemia: This is the term for abnormally high levels of homocysteine in the blood or urine.
  • Cardiovascular diseases: This may include coronary heart disease, blood clots, stroke, and heart attack.
  • Birth abnormalities: This may include neural tube defects or conditions such as microcephaly, in which the head is smaller than expected at birth.
  • Dementia: Dementia involves symptoms of cognitive decline, such as memory loss, confusion, and mood changes.
  • Mental health conditions: People with the MTHFR gene variant may be at higher risk of depression.
  • Drug-induced toxicity: People with the MTHFR gene variant may have a higher risk of toxicity from medication affecting folate homeostasis, such as methotrexate (MTX).
  • Peripheral neuropathy: This is a neurological condition that damages the nerves.

Symptoms vary among individuals and depend on the type of mutation someone has. People may not know they have an MTHFR mutation unless they experience severe symptoms or undergo genetic testing.

Having one or two MTHFR mutations can increaseTrusted Source the levels of homocysteine, an amino acid that the body produces by breaking down dietary proteins, present in the blood. This condition is called hyperhomocysteinemia.

High levels of homocysteine can damage blood vessels and lead to blood clots. People who have high homocysteine levels may haveTrusted Source low levels of vitamin B12.

Complications research associatesTrusted Source with having hyperhomocysteinemia due to MTHFR mutations include:

  • abnormal blood clotting
  • developmental delays
  • eye problems, such as glaucoma
  • anencephaly, a birth abnormality in which the brain and skull do not form properly

A doctor can determine whether or not a person has an MTHFR variant by reviewing their medical history, considering their current symptoms, and performing a physical examination.

The doctor may recommend running a blood test to check the person’s homocysteine levels. It is also possible to identify an MTHFR gene mutation through genetic testing.

Doctors may recommendTrusted Source dietary and lifestyle changes to help offset any resulting nutritional deficiencies in people with an MTHFR variant.

For example, people with high homocysteine levels due to folate or vitamin B12 deficiencies can take folic acid or vitamin B12, respectively.

MTHFR mutations will not change a person’s treatment plan for any other condition they happen to have.

If a person with an MTHFR mutation has a blood clot, for example, they will usually receive the same treatment for the blood clot as someone who does not have this type of mutation.

Some sources might suggest that people with MTHFR gene variants should not consume folic acid. However, the Centers for Disease Control and Prevention (CDC)Trusted Source disputes this claim, stating that people with this variant can safely process all types of folate.

A 2017 studyTrusted Source of 4507 adults from China suggests that foods such as soy, salt, sugar, and fried foods may correlate with higher levels of homocysteine in the blood.

In contrast, fish, eggs, and milk may negatively correlate with homocysteine levels in the blood for some people. However, the strength of this correlation varied depending on gender and genotype. The authors suggest that further studies are necessary.

People can speak with a healthcare professional for more advice about foods to include in their diet and what to limit or avoid.

Having two copies of the MTHFR gene variant may increaseTrusted Source the risk of certain pregnancy complications.

Healthcare professionals may suggest taking folic acid supplements to reduce the risk of certain pregnancy complications, such as neural tube defects, whether or not someone has an MTHFR gene variant.

The CDC recommends that pregnant people take 400 micrograms (mcg)Trusted Source of folic acid daily.

Existing research has not shownTrusted Source that testing for an MTHFR mutation would have clinical value. For this reason, current guidelines from the American College of Medical Genetics and Genomics state not to screen for this mutation routinely.

People inherit one copy of the MTHFR gene from each of their parents, which means that everyone has two MTHFR genes. Mutations can occur in one or both of these genes.

Having a parent or close relative with an MTHFR gene mutation can increase a person’s risk of inheriting the same variant themselves.

People with two parents who have a mutation have an increased risk of having a homozygous MTHFR mutation.

A person should contact a doctor if they experience any symptoms of a folate or vitamin B12 deficiency, which may include:

A person should also contact a doctor if they experience any symptoms of anemia, which may include:

MTHFR mutations do not affect everyone in the same way. People with one or more MTHFR variants may have higher levels of homocysteine in their blood or urine.

Although existing research has identified associations between MTHFR variants and certain health conditions, more research is necessary to determine the exact effects of these gene mutations on health.

People can speak with a doctor about the benefits and risks of genetic testing or about dietary changes that may help to balance homocysteine levels.