On this page
- Start 400 mcg of folic acid daily at least one month before you try to conceive; USPSTF supports 400 to 800 mcg 1.
- CDC recommends 400 mcg every day for everyone who could become pregnant, planned or not 2.
- The neural tube closes about 26 to 28 days after fertilization, often before pregnancy is recognized 3.
- After a previous NTD-affected pregnancy, CDC recommends 4 mg daily starting one month before conception, with a clinician 6.
- Look for the words 'folic acid' on the Supplement Facts panel; it is the only form proven to prevent NTDs 6.
Start taking 400 mcg of folic acid every day at least one month before you try to get pregnant, and keep taking it through the first two to three months of pregnancy.12 CDC actually recommends 400 mcg daily for everyone who could become pregnant, because the baby's neural tube forms before most people know they are pregnant.23
This page covers when to start, how much to take, who needs a higher dose, how to choose a product, and a simple preconception checklist.
When should you start folic acid?
The short answer: at least one month before conception, and ideally any time pregnancy is possible.
- USPSTF recommends a daily supplement of 400 to 800 mcg starting at least one month before anticipated conception.13
- ACOG advises starting a prenatal vitamin with at least 400 mcg of folic acid at least one month before pregnancy when possible.4
- CDC recommends 400 mcg every day for everyone capable of becoming pregnant, not only those actively trying.2
The CDC approach covers unplanned pregnancies too. If pregnancy is possible at all, daily folic acid is the recommendation.
Why starting before pregnancy matters
The embryo's neural tube normally closes about 26 to 28 days after fertilization.35 That is often before a pregnancy is recognized.3
If you wait for a positive test, you may miss part or all of the window when folic acid helps most.3 Neural tube defects (NTDs) include spina bifida, anencephaly, and encephalocele, and USPSTF estimates they affect about 3,000 U.S. pregnancies each year.1
| Timeline | What is happening | Folic acid status |
|---|---|---|
| 1+ month before conception | Building up folate levels | Daily folic acid already started 1 |
| Conception | Fertilization | Keep taking it daily 1 |
| About days 26 to 28 after fertilization | Neural tube normally closes 3 | Protection depends on folate already on board |
| Positive test, first prenatal visit | Pregnancy often recognized after closure 3 | Starting now may miss part or all of the window 3 |
How much should you take before pregnancy?
The amount depends on whether you are at average or higher risk. These are separate recommendations.
| Your situation | Daily folic acid | Start | Who sets the dose |
|---|---|---|---|
| Average risk, could become pregnant | 400 mcg (USPSTF range 400 to 800 mcg) | Now, or at least 1 month before trying | You, following CDC/USPSTF 21 |
| Previous NTD-affected pregnancy | 4,000 mcg (4 mg) | 1 month before conception, through first 3 months | Your clinician 62 |
| Other higher-risk factors | Depends on guideline and situation | Plan at a preconception visit | Your clinician 71 |
Who counts as higher risk?
According to ACOG and USPSTF, factors that can raise NTD risk include:71
- A previous pregnancy affected by an NTD
- A personal, partner, or family history of NTDs
- Taking certain antiseizure medicines
- Malabsorption after bariatric surgery
- Diabetes present before pregnancy
- Obesity
If any of these apply, book a preconception visit rather than choosing a dose on your own.71 The 4 mg dose is far above the adult upper limit of 1,000 mcg a day of folic acid from supplements and fortified foods, which is why it needs a clinician.68
For the full breakdown of doses by stage, see how much folic acid for pregnancy.
Can food alone cover it?
Food helps, but it is not enough on its own for this purpose. Natural folate is found in leafy vegetables, beans and peas, asparagus, Brussels sprouts, avocado, citrus, nuts, liver, eggs, and other foods.68 Since 1998, many U.S. enriched grain products such as breads, flours, cereals, rice, and pasta have been fortified with folic acid.98
Even so, diet alone is not a reliable substitute for the specific 400 mcg folic acid recommendation. CDC advises combining folate-rich foods with a vitamin containing folic acid, fortified foods, or both.10 Folic acid is also the only form of folate shown in studies to help prevent NTDs.6
See our list of foods high in folic acid and folate to round out your diet.
Enriched vs whole grain
"Whole grain" and "enriched" are not synonyms. Mandatory folic acid fortification generally applies to standardized enriched grain products, so a whole-grain bread or pasta may contain natural folate but is not necessarily fortified unless the ingredient list or Nutrition Facts panel says so.116 Since 1998, fortified U.S. enriched grains have carried 140 mcg of folic acid per 100 g.98
How to choose a preconception supplement
Folic acid comes alone, in multivitamins, in B-complex products, and in prenatal vitamins.8 Any of these can work, as long as you check the label.
- Find the words "folic acid" on the Supplement Facts panel.210
- Read the amount in parentheses. A label might show "667 mcg DFE (400 mcg folic acid)." That means 400 mcg of folic acid, which equals about 667 mcg DFE when taken with food.8
- Do not assume that a product labeled "methylated," "food-based," or "prenatal" meets the recommendation.210
- Check the serving size so you know the daily amount.
Methylfolate and MTHFR
5-MTHF (methylfolate) is a real folate form, but it lacks the same direct NTD-prevention trial evidence as folic acid.62 People with common MTHFR variants can process folic acid, and CDC still recommends 400 mcg a day of folic acid for them.12 If your product lists only 5-MTHF, ask a pharmacist or obstetric clinician whether it fits your plan.12 Our page on methylfolate vs folic acid explains the difference.
Preconception folic acid checklist
Use this as a starting point for your own planning or a preconception visit:
- [ ] Start a product with 400 mcg folic acid daily now, or at least one month before trying.21
- [ ] Confirm the label says "folic acid" and shows the amount in parentheses.28
- [ ] Add folate-rich and fortified foods to your meals.10
- [ ] Ask about a higher dose if you have had an NTD-affected pregnancy or have another risk factor.67
- [ ] Tell your clinician and pharmacist about every medicine you take, especially antiseizure medicines, methotrexate, sulfasalazine, or trimethoprim.813
- [ ] Do not stack multiple prenatal vitamins to get more folic acid.7
- [ ] Keep taking it through the first two to three months of pregnancy.1
What folic acid will and will not do before pregnancy
Folic acid's established benefit is preventing NTDs, backed by randomized trials, observational studies, and fortification experience.21 After U.S. fortification began, NTD prevalence fell about 35%, and CDC estimated around 1,300 NTD-affected births were prevented each year.1516
It is not a fertility booster. Evidence does not support claims that folic acid improves fertility in people whose folate status is already adequate.8 And taking more than recommended is not known to add protection for average-risk people.12
Once you are pregnant, see when to stop taking folic acid in pregnancy for what changes after the first trimester, and our guide to neural tube defects for more on why this matters.
Frequently asked questions
How long before pregnancy should I start taking folic acid?
I just found out I am pregnant and have not taken folic acid. Is it too late?
Can I get enough folic acid from food when trying to conceive?
Food folate supports good nutrition, but diet alone is not a reliable substitute for the 400 mcg folic acid recommendation. CDC advises combining folate-rich foods with a vitamin containing folic acid, fortified foods, or both 10.
Does folic acid help you get pregnant?
Folic acid's proven role is preventing neural tube defects. Evidence does not support claims that it boosts fertility in people whose folate levels are already adequate 8.
Should my partner take folic acid too?
Sources
- U.S. Preventive Services Task Force (USPSTF). Folic Acid Supplementation to Prevent Neural Tube Defects: Recommendation.
- 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: Final Recommendation Statement.
- American College of Obstetricians and Gynecologists (ACOG). Healthy Eating During Pregnancy.
- NHS (UK National Health Service). Common questions about folic acid.
- Centers for Disease Control and Prevention (CDC). Folic Acid: Facts for Clinicians.
- American College of Obstetricians and Gynecologists (ACOG). Prepregnancy Counseling.
- NIH Office of Dietary Supplements. Folate - Health Professional Fact Sheet.
- U.S. Food and Drug Administration (FDA). Fortifying Corn Masa Flour Products with Folic Acid.
- Centers for Disease Control and Prevention (CDC). Folic Acid: Sources and Recommended Intake.
- U.S. Food and Drug Administration (FDA). Questions and Answers Regarding Fortification Policy.
- Centers for Disease Control and Prevention (CDC). MTHFR Gene Variant and Folic Acid Facts.
- MedlinePlus Magazine, NIH. Did You Know? Supplements and Medications Can Interact in Unexpected Ways.
- PubMed Central, NIH. Excess Folic Acid and Vitamin B12 Deficiency (Miller, 2024).
- Centers for Disease Control and Prevention (CDC). Updated Estimates of Neural Tube Defects Prevented by Mandatory Folic Acid Fortification (MMWR).
- Centers for Disease Control and Prevention (CDC). MMWR News Synopsis for January 15, 2015.
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.
