MTHFR Gene Test Test

An MTHFR gene test checks for two common changes in the MTHFR gene that can affect how your body processes folate. These changes may lead to high homocysteine levels, which could increase the risk of blood clots, heart disease, stroke, and pregnancy complications. However, having these gene changes does not necessarily cause health problems, and treatment for high homocysteine is usually the same regardless of test results.

What this test measures

An MTHFR gene test checks a sample of your blood for two very common changes in a gene called MTHFR. These changes are called C677T and A1298C. The MTHFR gene provides instructions for making a protein that helps your body use folate, a type of B vitamin.

What your results mean

Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.

Higher-than-normal results

A positive test result means you have an MTHFR gene change in one or both of your MTHFR genes. If your homocysteine levels are high and you have two copies of the C677T change or one copy each of C677T and A1298C, these changes are probably causing the increased homocysteine levels.

Lower-than-normal results

A negative test result means neither of the common MTHFR gene changes were found. If you have high homocysteine, it is probably from another condition such as a lack of B vitamins, certain medicines, older age, hypothyroidism, kidney disease, or another disease.

Frequently asked questions

What does an MTHFR gene test look for?

It looks for two common changes in the MTHFR gene called C677T and A1298C.

Does having an MTHFR gene change mean I will have health problems?

No, having either variant does not necessarily increase your risk for any health condition, nor does it guarantee high homocysteine levels.

How is high homocysteine treated?

Your provider will usually recommend vitamin B supplements that include folic acid. If you have the MTHFR variant, your provider may recommend methylfolate (5-MTHF) instead.

Should I take folic acid if I have an MTHFR variant and might become pregnant?

Yes, the CDC recommends folic acid supplements for everyone who may become pregnant, even if they have the MTHFR gene variant.

Is an MTHFR gene test always needed if I have high homocysteine?

Generally no, because treatment for high homocysteine is the same whether or not it is caused by an MTHFR variant.

Sources

MedlinePlus: MTHFR Gene Test — NIH MedlinePlus

Last updated July 7, 2026. Information is aggregated from official public sources and is not a substitute for professional medical care.