MTHFR Gene Test
Reviewed
Also called: methylenetetrahydrofolate reductase mutation, C677T and A1298C, MTHFR DNA assay, MTHFR DNA testing, MTHFR gene variants, MTHFR gene polymorphisms 677T>C & 1298A>C mutations
This test checks a sample of your blood for two common changes (variants) in the MTHFR gene, called C677T and A1298C. The MTHFR gene helps your body use folate (a B vitamin) to break down an amino acid called homocysteine. Having one of these gene changes does not necessarily increase your risk for any health condition, nor does it guarantee high homocysteine levels. The test is usually done only if a homocysteine blood test has already shown high levels, or if a newborn has a positive result in a routine homocystinuria screening test. However, many medical experts do not recommend routine testing for these common MTHFR gene changes because treatment for high homocysteine is the same regardless of the cause.
Specimen: blood
Why this test may be ordered
- You had a blood test showing higher than normal homocysteine levels and a close relative was diagnosed with an MTHFR gene change.
- You had a blood test showing higher than normal homocysteine levels and you and/or close family members have early heart or blood vessel disease.
- Your provider prescribes methotrexate (used for certain cancers, psoriasis, or rheumatoid arthritis) and wants to choose a safe dose.
- A newborn has a positive result in a routine homocystinuria screening test.
Preparation and collection
You don't need any special preparations for this test.
A health care professional will take a blood sample from a vein in your arm, using a small needle. This usually takes less than five minutes.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
Test results are usually reported as positive or negative. Your provider will interpret your results along with your homocysteine levels and other factors.
- Positive: You have an MTHFR gene change in one or both of your MTHFR genes. Having a change in only one gene is unlikely to cause any health problems. If your homocysteine levels are high and you have two copies of the C677T change or one copy each of C677T and A1298C, these gene changes are probably causing your increased homocysteine levels. If you have two copies of the A1298C change, your increased homocysteine levels are probably not caused by these gene changes. Limitation: Having a positive result does not guarantee that you will have high homocysteine levels or develop any health condition. Researchers are not certain that increased homocysteine levels directly cause health problems. Next step: If your homocysteine levels are high, your provider will usually recommend vitamin B supplements (including folic acid) to lower them. If you have the MTHFR variant, your provider may recommend methylfolate (5-MTHF) instead. Talk with your provider before making any changes.
- Negative: Neither of the common MTHFR gene changes (C677T or A1298C) were found in your blood sample. If you have increased homocysteine levels, it is probably from another condition, such as a lack of B vitamins, taking certain medicines, older age, hypothyroidism, kidney disease, or another disease. Limitation: A negative result does not rule out rare MTHFR gene changes that can cause a genetic disease called homocystinuria. Different types of gene tests are used to look for those rare changes. Next step: Your provider will work with you to determine the cause of any high homocysteine levels and recommend appropriate treatment, which may include vitamin B supplements.
- Having an MTHFR gene variant does not necessarily increase your risk for any health condition, nor does it guarantee that you will have high homocysteine levels.
- Researchers are not certain whether homocysteine levels affect your risk for developing blood clots or early heart or blood vessel disease.
- Because of this uncertainty, some medical experts recommend against using MTHFR testing for this purpose.
- A negative result for common variants does not rule out rare MTHFR gene changes that can cause homocystinuria.
What to do next
If you have questions about your results, talk with your provider. Do not make changes to your health habits without first discussing them with your provider. The U.S. Centers for Disease Control and Prevention (CDC) recommends folic acid supplements for everyone who may become pregnant, even if you have an MTHFR gene variant.
- What do my MTHFR test results mean for my health?
- Do I need a homocysteine blood test?
- Should I take vitamin B supplements, and if so, which type?
- How often should I have my homocysteine levels checked?
- Do I need to see a genetic counselor?