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Folic acid supplement: who should take it, and how much

By the Life in Good Form editors. Updated 2026-10-15.

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Who should take folic acid

CDC says all women capable of becoming pregnant should get 400 mcg of folic acid daily. The reason is timing: NIH explains that neural tube defects occur within 28 days after conception, when many people do not yet know they are pregnant. Women with low folate intake are at higher risk of having a baby with a neural tube defect.

If you had a past pregnancy affected by a neural tube defect and plan another pregnancy, CDC says to talk with your doctor first. The recommended amount for that group is much higher, 4,000 mcg a day, starting a month before pregnancy and through the first three months. That higher dose is a medical plan, not something to start on your own.

For pregnancy itself, a prenatal vitamin usually covers folic acid; see our prenatal vitamin guide.

Folic acid vs folate vs methylfolate

Folate is the form found naturally in foods such as spinach, liver, asparagus and brussels sprouts. Folic acid is the synthetic form used in supplements and in fortified grains. Since January 1998, FDA has required 140 mcg of folic acid per 100 g to be added to enriched breads, cereals, flours, corn meal, pasta and rice.

Methylfolate (5-MTHF) is another supplement form. NIH notes that folic acid is the form proven to reduce neural tube defect risk. If you are comparing the two, our methylfolate guide covers that choice in detail.

Watch for listings that call methylfolate "folic acid." Read the Supplement Facts panel for the actual form.

How to read mcg and DFE on the label

Labels now show folate in mcg of dietary folate equivalents (DFE), often with the folic acid amount in parentheses. NIH defines the conversion: 1 mcg DFE equals 0.6 mcg of folic acid taken with food, or 0.5 mcg taken on an empty stomach.

The DFE figures are simple arithmetic from NIH's conversion. The adult RDA is 400 mcg DFE, rising to 600 mcg DFE in pregnancy and 500 mcg DFE while breastfeeding.

The upper limit and the vitamin B12 question

NIH sets the adult upper limit at 1,000 mcg a day of folic acid from supplements and fortified foods. Food folate does not count toward it.

The limit exists because of vitamin B12. NIH explains that large amounts of folate can correct the anemia of B12 deficiency but not its nerve damage, so experts worried that high folic acid could hide B12 deficiency until damage became permanent. Concern has shifted to the possibility that large amounts of folate could worsen the anemia and cognitive symptoms of B12 deficiency. If you may have low vitamin B12, ask your doctor before taking high-dose folic acid.

Medicines that interact with folic acid

NIH lists several:

• Methotrexate: people taking it for cancer should consult their oncologist before folate supplements, because they could interfere with its effect. For low-dose methotrexate in rheumatoid arthritis or psoriasis, folate may reduce stomach side effects, under a doctor's direction.
• Antiepileptic drugs such as phenytoin, carbamazepine and valproate can lower folate levels, and folate supplements might lower blood levels of these drugs. Check with your provider first.
• Sulfasalazine reduces folate absorption; ask whether you need a supplement.

How to choose a folic acid supplement

• For pregnancy prevention planning, 400 mcg is enough for most people; a higher dose only on medical advice.
• Check your multivitamin first. Many already include 400 mcg, and adding a separate tablet doubles it.
• Read the form on Supplement Facts: folic acid, not methylfolate, if you want the form studied for neural tube defects.
• Look for a verifiable quality mark such as USP or NSF. FDA does not approve supplements for safety and effectiveness before sale.

What to look for when you buy

Questions people ask

Should all women take a folic acid supplement?

CDC recommends 400 mcg daily for anyone who could become pregnant, even if not planning to, because neural tube defects form very early in pregnancy.

What is the best folic acid supplement?

A plain 400 mcg folic acid tablet, or a multivitamin or prenatal that already contains it. Higher doses are only needed with medical advice.

Can you take too much folic acid?

Adults should keep folic acid from supplements and fortified foods under 1,000 mcg a day unless prescribed more, mainly because of interactions with vitamin B12 deficiency.

Is folic acid the same as folate?

Folate is the natural form in food; folic acid is the synthetic form in supplements and fortified grains. Folic acid is the form proven to lower neural tube defect risk.

Sources

• Folate: Fact Sheet for Health Professionals (ods.od.nih.gov), NIH Office of Dietary Supplements
• Dietary Supplements and Life Stages: Pregnancy (ods.od.nih.gov), NIH Office of Dietary Supplements
• About Folic Acid (cdc.gov), Centers for Disease Control and Prevention
• Information for Consumers on Using Dietary Supplements (fda.gov), U.S. Food and Drug Administration

Sources checked 2026-10-15.