If you’ve been told you have an MTHFR gene variant, or you’ve read that you should avoid folic acid, you’re not alone. It’s one of the most common questions about folic acid. The CDC’s answer is clear: people with an MTHFR variant can still take folic acid, and it still works.

The short version

  • You can take folic acid. People with an MTHFR variant can process all types of folate, including folic acid, according to the CDC.
  • 400 mcg a day is still the recommendation if you could become pregnant. Folic acid is the only type of folate shown to help prevent neural tube defects (NTDs).
  • How much you take matters more than your gene. Folic acid intake is a stronger factor in your blood folate than having a variant.
  • Variants are common and normal. More people in the U.S. have one or two copies of the most common variant than have none.
  • You don’t need an MTHFR test. The American College of Medical Genetics and Genomics advises against routine MTHFR testing.
  • You don’t need methylfolate because of a variant. It hasn’t been shown to prevent NTDs.

What the MTHFR gene is

The MTHFR gene gives your body instructions for making a protein that helps process folate. Your body needs folate to make DNA and to modify proteins, according to the CDC.

A gene variant is a change in the DNA sequence that’s different from the expected one. Variants are part of what makes people different from one another, like eye color or blood type. Everyone has two copies of the MTHFR gene, one from each parent.

The two common variants are:

  • C677T, the most common one. Your two copies can be CC (no variant), CT (one copy), or TT (two copies).
  • A1298C, another common variant.

Very rare MTHFR variants also exist, and they can have significant effects on health. If you have concerns about one of those, the CDC advises talking with your doctor or a genetic counselor.

How common are they?

More people in the U.S. have one or two copies of C677T than don’t. The variant is more common in some groups: Hispanic people are more likely than non-Hispanic White or non-Hispanic Black people to have it, according to the CDC. Having a variant doesn’t mean something is wrong.

Folic acid still works with a variant

You may have heard that you should avoid folic acid if you have an MTHFR variant and take another form of folate, such as 5-MTHF, instead. The CDC says that isn’t true. It found:

  • Blood folate is only slightly lower. At the same folic acid intake, people with the TT genotype have an average blood folate level about 16% lower than people with the CC genotype.
  • Folic acid raises blood folate for everyone. Studies show that 400 mcg a day increases blood folate whatever your MTHFR genotype.
  • A1298C alone doesn’t appear to matter much. There isn’t enough evidence that the A1298C variant by itself significantly changes how the body processes folate.
  • Common variants aren’t a reason to avoid folic acid.

The CDC says the two most important factors in having enough folate to help prevent an NTD are how much folic acid you take each day, from vitamins and fortified foods, and how long you take it before pregnancy. That’s why starting at least a month ahead matters. See When to Start Taking Prenatal Vitamins.

Taking folic acid at the recommended amounts hasn’t been shown to cause harm. More isn’t necessarily better for preventing NTDs, though a doctor might recommend more than 400 mcg if you have other health conditions.

What about methylfolate?

Methylfolate (also written 5-MTHF or L-methylfolate) is a form of folate sold in some supplements and prenatal vitamins. It hasn’t been tested in clinical trials for preventing NTDs, according to the NIH, while folic acid is the form that has. About 1 in 4 over-the-counter prenatals and 1 in 3 prescription ones contain methylfolate in place of folic acid. If yours lists only methylfolate, ask your provider whether it fits your needs. See Prenatal Vitamin Questions, Answered.

Should you be tested?

Not as a routine matter. The American College of Medical Genetics and Genomics concluded in 2013 that MTHFR testing has minimal clinical use. Its recommendations, as summarized by the National Library of Medicine’s GeneReviews:

  • MTHFR testing shouldn’t be part of the workup for blood clotting problems or recurrent pregnancy loss.
  • It shouldn’t be ordered for family members just because a relative has a variant.
  • MTHFR status doesn’t change the recommendation that women of childbearing age take the standard dose of folic acid to reduce the risk of NTDs.

The same review notes that the more common genotypes are unlikely to matter clinically, and that people with two copies of C677T and normal homocysteine levels don’t have a higher risk of venous blood clots or recurrent pregnancy loss.

Common questions

I was told to avoid folic acid. Now what? Keep taking it and bring this page, or the CDC’s page, to your next visit. The CDC says people with a common MTHFR variant can process folic acid, and it’s the form proven to prevent NTDs. If your provider has a specific reason for a different plan, such as a rare variant or another health condition, ask them to explain it.

Do I need a higher dose? Not because of a common variant. The CDC says more than 400 mcg isn’t necessarily better for preventing NTDs, though a doctor may recommend more if you have other conditions. If you’ve had a pregnancy affected by an NTD, the recommendation is different. See Why Folic Acid Matters in Pregnancy.

Does MTHFR cause miscarriage or blood clots? The evidence says no for the common variants. The ACMG reviewed the research and found no association between MTHFR variants and venous blood clots, and it advises against MTHFR testing as part of an evaluation for recurrent pregnancy loss. If you’ve had pregnancy losses, ask your provider about the tests that are recommended.

Should I take a home MTHFR test? There’s no medical reason to. Routine testing isn’t recommended, and the result wouldn’t change the folic acid advice.

I already have a result that says I have a variant. That’s very common. Keep taking 400 mcg of folic acid a day if you could become pregnant, and mention the result to your provider. If it’s a rare variant, ask for a referral to a genetic counselor.

What to do now

  • Take 400 mcg of folic acid every day if you could become pregnant, and check your labels for “folic acid.”
  • Start at least 1 month before you try to get pregnant.
  • If your prenatal lists only methylfolate, ask your provider about it.
  • Skip MTHFR testing unless your provider has a specific medical reason.
  • Talk with your doctor or a genetic counselor if you have a rare variant or questions about your family history.

Related reading

Sources

Updated November 2026. This article is for general information and is not a substitute for advice from your health care provider.