MTHFR test: what it can and can’t tell you about folate

MTHFR is a gene that helps your body process folate, a B vitamin it needs to make DNA.^[2] The gene carries the instructions for an enzyme, methylenetetrahydrofolate reductase, that turns folate into the form found most in your blood.^[1] Everyone has two copies of the gene, one from each parent.^[2]

It’s the everyday name for a common variant in the gene: a spot where a single letter of its DNA differs. The best known is C677T, where a C is replaced by a T at position 677.^[2] The word “mutation” can sound alarming, but this one is common: in the US, more people carry it, in one copy or two, than don’t.^[2] MedlinePlus calls it a polymorphism, the term for a variant this common.^[1] Carrying it isn’t a diagnosis. One copy or two explains what each result means for folate.

Mostly because the guideline that covers it found little evidence that a result is clinically useful (see what the genetics guideline says).^[3] The common variants are also widespread and make only a small difference to folate.^[2] MedlinePlus notes that medical experts don’t recommend testing for these common changes in most cases.^[4] So it isn’t that doctors don’t take MTHFR seriously.

An MTHFR test is a genetic test that reads your MTHFR gene to see which of its common variants you carry. The most studied is C677T.

GeneHealth’s wellness report reads one of these variants, MTHFR C677T, and only for how your body processes folate.

For general wellness and information, not diagnosis.

With a DNA test, often called an MTHFR gene test. A lab checks the gene in a blood or saliva sample and reports whether you carry no copies, one copy or two copies of a common variant such as C677T. Clinic labs and home kits both offer it. Guidelines advise against routine MTHFR testing.^[3]

Yes, if you mean which variants you carry: the MTHFR gene test itself, a DNA test rather than a diagnosis. In a clinic it’s usually done on a blood sample.^[4] Because it reads the DNA you inherited, which is the same in your saliva as in your blood, a saliva sample can be read for the same gene. No other kind of blood test can show which MTHFR variants you carry.

Yes, with no needle or appointment. GeneHealth is one home option: you collect a saliva sample by gently rubbing a soft swab along your gums, activate the kit, and post it back to our own CLIA-certified laboratory in Chicago (New York orders excepted). It reads just one variant, MTHFR C677T, and only to describe how your body processes folate. Results are usually ready 5 to 7 business days after the lab receives your activated sample (10 to 14 business days during holiday weeks).

For general wellness and information, not diagnosis.

It depends on the lab and on what else the test reads; our guide to genetic testing cost explains why prices vary. At GeneMatrix, your MTHFR result comes inside a wider wellness report, at one price paid once when you order: GeneHealth is $199, and GeneCore, the all-in-one, is $499.

For general wellness and information, not diagnosis.

The C677T variant changes a single letter of the gene, and the enzyme made from it is less active.^[1] That can sound as if carriers can’t use folate. They can: the CDC says people with MTHFR variants can process all types of folate, including folic acid.^[2]

The CDC also points out that your MTHFR type affects your blood folate level less than how much folic acid you get.^[2] So a result tells you about an inherited trait, not about the folate you have right now.

A C677T result counts how many of your two copies of the gene carry the variant: none, one or two. Even with two copies, average blood folate is only slightly lower than with none.^[2] Having two copies isn’t rare: an estimated 25 percent of Hispanic people and 10 to 15 percent of white North Americans have it.^[1]

Being heterozygous for MTHFR C677T means one of your two copies of the gene carries the variant and the other doesn’t, so your result reads CT. It’s a common result, and people with an MTHFR variant can still process every type of folate, folic acid included, the CDC says.^[2]

For most people there is little reason to. The American College of Medical Genetics and Genomics advises against routine MTHFR testing, having found little evidence that the results are clinically useful.^[3]

If you are simply curious about the trait, a wellness report can describe it, read as information rather than advice. If you have a health concern, talk to your clinician, who can choose the tests that fit it.

• Your folate level. A gene result isn’t a measure of the folate in your blood.
• What to eat. It can’t choose a diet for you.
• Anything about your health. It describes a trait you were born with. It doesn’t diagnose a condition, and it isn’t a medical test.
• What will happen to you. Findings on the gene come from studies of groups, so they describe averages, not one person.

GeneHealth’s report has a Folate trait: it reads one variant, MTHFR C677T, and describes how your body processes folate. GeneCore, the all-in-one, has a folate trait in its health area too. Both are among our DNA nutrition tests.

For general wellness and information, not diagnosis.

Both are one-time tests from a saliva sample you collect at home, for general wellness and information. To see a whole report first, look at the sample report.