Told to Avoid Folic Acid for MTHFR? What the CDC Says

Yes, you can take folic acid if you have an MTHFR gene variant, and it still works. The CDC says people with an MTHFR gene variant can process all types of folate, including folic acid. It still advises 400 mcg a day for anyone who could become pregnant.

Maybe a test result came back with "MTHFR" on it. Maybe a post told you that folic acid is a synthetic toxin your body can't use, and that you need methylfolate instead. If you're trying to conceive, or simply could, that kind of warning lands hard. Here is what the evidence says, including the part most of those posts leave out.

What Does the MTHFR Gene Do?

MTHFR makes an enzyme that turns folate into the active form your cells use. Common variants, the best known being C677T, make that enzyme work less efficiently.

Having one copy of C677T is ordinary. The CDC says more people in the United States have one or two copies of it than don't. Having two copies (called TT) is less common, and it's the version that matters most.

The NIH Office of Dietary Supplements says two copies are linked to elevated homocysteine levels and an increased risk of NTDs. NTDs are neural tube defects, serious birth defects of the brain and spine such as spina bifida. That risk is the reason the MTHFR worry spread in the first place.

Who Is Most Likely to Carry Two Copies?

It depends a lot on ancestry. The NIH estimates that about 25% of Hispanic people carry two copies of C677T. The figure is 10% for white and Asian people and 1% for African American people.

So carrying two copies, the version most posts warn about, is rare in Black women. If you're Black and planning a pregnancy, MTHFR is very unlikely to be the thing standing between you and enough folate. The standard advice applies to you exactly as written.

For Hispanic and Latina women, the picture is different, and it's where the methylfolate story breaks down most clearly. The NIH notes that neural tube defect rates in the US are highest among Hispanic women and lowest among non-Hispanic Black women. That sounds like proof that genes are the problem. The intake data tells a different story.

Why Intake Matters More Than Your Genes

The CDC states it directly: your folic acid intake is more important than your MTHFR genotype for the amount of folate in your blood. On the same intake, people with two copies have blood folate that is only slightly lower than people with none.

Now look at how much folic acid women are getting. The CDC says Hispanic/Latina women are less likely to get folic acid from fortified foods or to take a multivitamin with folic acid.

In 2016 the FDA allowed folic acid to be added to corn masa flour, the base of tortillas and tamales, to close that gap. It was voluntary. Many Hispanic women don't eat much of the other fortified grain products. A 2024 study using national survey data compared nonpregnant Hispanic women of reproductive age before fortification (2011 to 2016) and after (2017 to March 2020).

Nothing moved. The share getting under 400 mcg of folic acid a day was 86.1% before and 87.8% after. The share with red blood cell folate below the level linked to the best protection stayed around 16% to 18%.

The researchers estimated that better folate status in this group could prevent about 157 neural tube defects a year, though the range was wide. That gap is about intake. Switching the form of folate wouldn't close it, because most women in the study weren't getting 400 mcg of folic acid to begin with.

If corn masa is a staple for you, check the label. The CDC notes that specific corn masa flours may or may not contain added folic acid. Either way, a daily supplement doesn't depend on what's in the bag.

Is Methylfolate Better Than Folic Acid?

Not for preventing neural tube defects. Methylfolate, also labeled 5-MTHF or L-methylfolate, is a real and usable form of folate. The NIH says its bioavailability in supplements is the same as or greater than that of folic acid.

The problem is what's been tested. Folic acid is the only form of folate shown to help prevent neural tube defects, according to the CDC. On the claim that people with MTHFR variants should take 5-MTHF instead, the CDC's verdict is short: "this is not true."

The NIH adds that research on whether people with the variant benefit from extra folate is inconclusive. So methylfolate is a usable form of folate, and people with the variant might benefit from it. It just hasn't been shown to prevent neural tube defects the way folic acid has. If your prenatal uses methylfolate in place of folic acid, ask your doctor or pharmacist whether it covers what you need.

Folic Acid vs Folate From Food

Folate is the form found naturally in food. Folic acid is the form used in supplements and fortified foods. Your body absorbs them differently.

The NIH estimates at least 85% of folic acid is bioavailable when taken with food, and nearly 100% on an empty stomach. Only about 50% of the folate naturally present in food is. Spinach, liver, asparagus and Brussels sprouts are among the richest food sources.

Food folate counts toward your daily total, and it's worth eating. But the pregnancy advice is specifically about folic acid, because that's the form behind the evidence. If you plan to eat more liver for its folate, read up on vitamin A in pregnancy first.

When Should You Start Taking Folic Acid?

Before you're pregnant, ideally at least a month before. The neural tube closes very early. The NIH says neural tube defects happen when it fails to close on days 21 to 28 after conception.

That's often before a missed period. The CDC says these defects happen in the first few weeks, often before you know you are pregnant. The NIH estimates about half of US pregnancies are unplanned.

This is the real cost of the MTHFR scare. If a woman stops folic acid while she waits for a test result, or a new product, she can lose exactly those weeks.

The US Preventive Services Task Force updated its advice in 2023. It recommends a daily supplement containing 0.4 to 0.8 mg (400 to 800 mcg) of folic acid for anyone who plans to or could become pregnant. That's its highest grade, A.

For that update, the Task Force reviewed newer evidence, including three observational studies on neural tube defects. In a large Norwegian cohort, women who took folic acid before and during pregnancy between 2006 and 2013 had about half the risk. No effect showed up in the earlier years. It also looked for harms, including twins, autism and maternal cancer, and concluded that folic acid at usual doses is not linked to serious harms.

Should You Get an MTHFR Test?

For most women, no. The American College of Medical Genetics and Genomics concluded in 2013 that MTHFR polymorphism testing has minimal clinical utility. It reaffirmed that position in 2020.

The reason is simple. The folic acid advice is the same whatever the result says, so a positive test rarely changes what you should do. The ACMG review also found that earlier links to blood clots no longer show up in North American studies, possibly because of folic acid fortification.

The Task Force does list genetic changes in folate-related enzymes among the risk factors to raise with a clinician. So if you already know you carry two copies, mention it at a preconception visit. Just don't let the result talk you out of folic acid.

There's one exception worth knowing. The CDC notes that there are other, extremely rare MTHFR variants that can have significant effects on health. If you've been told you have one of those, talk to your doctor or a genetic counselor.

Can You Take Too Much Folic Acid?

Yes, which is why more isn't better. The NIH says adults shouldn't take more than 1,000 mcg a day from supplements and fortified foods, unless a doctor advises it. Food folate doesn't count toward that limit.

The main worry is vitamin B12. The NIH explains that large amounts of folate can correct the anemia of low B12 but not the nerve damage. That could hide a deficiency until the damage can't be reversed.

Low B12 is more likely in some groups. The NIH lists older adults, people with pernicious anemia or gastrointestinal disorders, people who've had stomach or bowel surgery and vegetarians. Long-term metformin or acid-reducing drugs called proton pump inhibitors also raise the risk.

If any of those apply, ask for a B12 check. Why low B12 can leave you exhausted on a good diet covers the testing in more detail.

You may also see warnings about "unmetabolized folic acid" building up in your blood. It does show up at higher intakes. The NIH says whether it has any biological activity is not known, and the questions about it are still unresolved.

Who Needs a Higher Dose of Folic Acid?

Some women need more than 400 mcg, but that's a decision to make with a doctor. If you've had a pregnancy affected by a neural tube defect, the CDC's current advice is 4,000 mcg a day. Start a month before trying again and continue through the first three months.

The Task Force lists other reasons to talk to a clinician about your dose:

• a personal, partner or family history of neural tube defects
• poor absorption after weight-loss surgery
• certain antiseizure medicines
• known changes in folate-related genes

It also notes that diabetes before pregnancy and obesity are linked to a higher risk. Don't raise your dose on your own, because of the B12 issue above.

When to See a Doctor

Book a preconception visit if you're planning a pregnancy and any of the risk factors above apply to you. Bring a list of everything you take, including your prenatal, so your doctor can check the folic acid total.

See a doctor soon if you have numbness or tingling in your hands or feet. The NIH says these nerve symptoms of low B12 can appear without anemia, so early diagnosis matters.

If you're already pregnant and haven't been taking folic acid, start now and tell your doctor or midwife. The CDC's advice covers early pregnancy, not only the weeks before it. For what else changes in your needs, choline in pregnancy is often missed in prenatals too.

Frequently Asked Questions

Can You Take Folic Acid With MTHFR?

Yes. The CDC says people with MTHFR variants can process folic acid. It recommends 400 mcg daily for anyone who could become pregnant, with or without a variant.

Is Methylfolate Safer Than Folic Acid in Pregnancy?

There's no evidence it is safer. It's well absorbed, but folic acid is the only form shown to help prevent neural tube defects. If your prenatal uses methylfolate, ask your doctor whether to switch.

Do You Need a Special Prenatal if You Have MTHFR?

No. A daily supplement with 400 mcg of folic acid meets the CDC advice, variant or not. Keep your total from supplements and fortified foods under 1,000 mcg unless a doctor advises more.