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- Adult RDA: 400 mcg DFE a day; pregnancy 600 mcg DFE; breastfeeding 500 mcg DFE.
- Anyone who could become pregnant: 400 mcg of folic acid daily, from at least one month before conception.
- Adult upper limit: 1,000 mcg a day of folic acid from supplements and fortified foods.
- After a previous NTD-affected pregnancy, CDC recommends 4,000 mcg (4 mg) a day under clinician guidance.
Folic acid is the manufactured form of vitamin B9 (folate) used in supplements and fortified foods; adults need 400 mcg DFE of folate a day, and anyone who could become pregnant should take 400 mcg of folic acid daily.12 This fact sheet puts the key numbers, top foods, risk groups, and safety limits on one page, with links to deeper guides.
For the full explanation of each topic, start with our folic acid guide.
Key numbers at a glance
| Fact | Number | Source |
|---|---|---|
| Adult RDA (19+) | 400 mcg DFE/day | NIH ODS 1 |
| Pregnancy RDA | 600 mcg DFE/day | NIH ODS 1 |
| Breastfeeding RDA | 500 mcg DFE/day | NIH ODS 1 |
| Daily folic acid if you could become pregnant | 400 mcg folic acid/day | CDC 2 |
| USPSTF supplement range before and in early pregnancy | 400 to 800 mcg/day | USPSTF 3 |
| After a previous NTD-affected pregnancy | 4,000 mcg (4 mg)/day, clinician-guided | CDC 2 |
| Adult upper limit (supplements + fortified foods) | 1,000 mcg folic acid/day | NIH ODS 1 |
| Daily Value on U.S. labels (age 4+) | 400 mcg DFE | NIH ODS 1 |
| U.S. fortification level, enriched grains | 140 mcg per 100 g (since 1998) | FDA, NIH ODS 41 |
| Neural tube closure | About 26 to 28 days after fertilization | USPSTF, NHS 56 |
| Body stores | About 15 to 30 mg, roughly half in the liver | NIH ODS 1 |
DFE conversions
Dietary Folate Equivalents (DFE) account for folic acid being better absorbed than food folate.1
| Source | 1 mcg DFE equals |
|---|---|
| Natural food folate | 1 mcg food folate |
| Folic acid with food | 0.6 mcg folic acid |
| Folic acid on an empty stomach | 0.5 mcg folic acid |
Source: NIH Office of Dietary Supplements.1
Quick check: 400 mcg of folic acid with food is about 667 mcg DFE, and 1 mg equals 1,000 mcg.1 Our folate DFE calculator does the math for any label.
Upper limits by age
These limits apply to folic acid from supplements and fortified foods, not to natural food folate.1
| Age | Upper limit |
|---|---|
| Birth to 12 months | Not established |
| 1 to 3 years | 300 mcg/day |
| 4 to 8 years | 400 mcg/day |
| 9 to 13 years | 600 mcg/day |
| 14 to 18 years | 800 mcg/day |
| Adults 19+, including pregnancy | 1,000 mcg/day |
Source: NIH Office of Dietary Supplements.1 For what happens above these levels, see how much folic acid is too much.
Top food sources
| Food and serving | mcg DFE |
|---|---|
| Beef liver, braised, 3 oz | 215 |
| Spinach, boiled, 1/2 cup | 131 |
| Black-eyed peas, boiled, 1/2 cup | 105 |
| Cereal fortified with 25% DV | 100 |
| Enriched white rice, cooked, 1/2 cup | 90 |
| Asparagus, boiled, 4 spears | 89 |
| Brussels sprouts, boiled, 1/2 cup | 78 |
| Enriched spaghetti, cooked, 1/2 cup | 74 |
Source: NIH Office of Dietary Supplements.1 See all 17 in foods high in folic acid and folate.
Who needs it most
- Anyone who could become pregnant: 400 mcg of folic acid daily, from supplements, fortified foods, or both, plus food folate.72
- People planning pregnancy: start at least one month before conception and continue through the first two to three months.3 Details are in folic acid for pregnancy.
- People at higher NTD risk: previous NTD-affected pregnancy, family history, certain antiseizure medicines, bariatric surgery, pregestational diabetes, or obesity need clinician counseling.83
- People at higher risk of deficiency: low intake, alcohol use disorder, celiac disease, inflammatory bowel disease, bariatric surgery, and some medicines.1
Forms in one line each
- Folate: the whole vitamin B9 family, including food forms.1
- Folic acid: the stable manufactured form; the only form shown to help prevent NTDs.19
- 5-MTHF (methylfolate): another supplement form; no formal DFE factor established.1
- Folinic acid (leucovorin): a prescription drug, not a substitute for folic acid.10
Safety facts
- 400 mcg a day has not been shown to cause harm, and USPSTF found no serious harms from usual doses.113
- Minor effects can include nausea, reduced appetite, gas, or bloating.12
- More than recommended is not known to improve NTD protection for average-risk people.1311
- Unexplained anemia should be checked for vitamin B12 deficiency before treating with folic acid.141
- Common MTHFR variants are not a reason to avoid folic acid.13
- No best time of day; consistency matters more. Do not double a missed dose.1512
Myths vs facts
| Myth | Fact |
|---|---|
| MTHFR means you cannot process folic acid | People with common MTHFR variants can process folic acid and should not avoid it on that basis 13 |
| Methylfolate is proven better for preventing birth defects | Folic acid is the only form directly shown to prevent NTDs 29 |
| More folic acid prevents more birth defects | Above recommended amounts, more benefit is not established for average-risk people 13 |
| Folic acid masks B12 deficiency at any dose | The concern is mainly high-dose treatment without B12 testing; fortification has not been shown to delay detection 111 |
| Folic acid causes autism | USPSTF found no increased autism risk from usual-dose supplements 3 |
| Folate and iron are the same thing | They are distinct nutrients 161 |
| Folinic acid and folic acid are interchangeable | Folinic acid (leucovorin) is a separate prescription drug 10 |
Reading a label in 30 seconds
- Find "Folate" on the Nutrition Facts or Supplement Facts panel. The first number is in mcg DFE.1
- Look in the parentheses. If it says "folic acid," that number is the actual folic acid amount, for example "667 mcg DFE (400 mcg folic acid)."1
- For pregnancy planning, check that the folic acid amount is typically 400 mcg.27
- If the form is methylfolate, the DFE number may use a different conversion factor of up to 1.7, so compare the actual amount.1
- Add up folic acid from all supplements and fortified foods if you take more than one product; the adult limit is 1,000 mcg a day.1
Evidence grades in brief
| Claim | Grade |
|---|---|
| Prevents neural tube defects | Established 3 |
| Treats folate-deficiency anemia | Established 17 |
| Prevents heart attacks | Mixed (modest stroke effect in some low-folate groups) 111 |
| Prevents dementia or cancer | Unsupported 111 |
| Boosts hair, energy, or fertility | Unsupported without a deficiency 1 |
Frequently asked questions
What are 5 facts about folic acid?
Folic acid is the manufactured form of vitamin B9 1. Adults need 400 mcg DFE of folate a day 1. Anyone who could become pregnant should take 400 mcg of folic acid daily 2. It is the only form of folate shown to help prevent neural tube defects 9. The adult upper limit from supplements and fortified foods is 1,000 mcg a day 1.
What is the difference between mcg and mcg DFE?
Who needs folic acid the most?
Can you take too much folic acid?
Yes, it is possible to exceed the adult upper limit of 1,000 mcg a day from supplements and fortified foods 1. Taking more than recommended does not give average-risk people better protection against birth defects 13. Higher doses should only be used for a specific medical reason with a clinician 1.
Sources
- NIH Office of Dietary Supplements. Folate - Health Professional Fact Sheet.
- Centers for Disease Control and Prevention (CDC). About Folic Acid.
- U.S. Preventive Services Task Force (USPSTF). Folic Acid Supplementation to Prevent Neural Tube Defects: Recommendation.
- U.S. Food and Drug Administration (FDA). Fortifying Corn Masa Flour Products with Folic Acid.
- U.S. Preventive Services Task Force (USPSTF). Folic Acid Supplementation to Prevent Neural Tube Defects: Final Recommendation Statement.
- NHS (UK National Health Service). Common questions about folic acid.
- Centers for Disease Control and Prevention (CDC). Folic Acid: Sources and Recommended Intake.
- American College of Obstetricians and Gynecologists (ACOG). Prepregnancy Counseling.
- Centers for Disease Control and Prevention (CDC). Folic Acid: Facts for Clinicians.
- MedlinePlus, U.S. National Library of Medicine. Leucovorin Injection: Drug Information.
- Centers for Disease Control and Prevention (CDC). Folic Acid Safety, Interactions, and Health Outcomes.
- NHS (UK National Health Service). About folic acid.
- Centers for Disease Control and Prevention (CDC). MTHFR Gene Variant and Folic Acid Facts.
- PubMed Central, NIH. Excess Folic Acid and Vitamin B12 Deficiency (Miller, 2024).
- NHS Specialist Pharmacy Service. Using folic acid with methotrexate in rheumatoid arthritis.
- National Heart, Lung, and Blood Institute (NHLBI). Anemia in Brief.
- NHS (UK National Health Service). Folic Acid: Medicine Information.
This article is for general education and is not medical advice. Doses and needs differ from person to person, so talk with your clinician or pharmacist about your situation. Read our editorial policy and medical disclaimer.
