Folate is needed for cell division and to prevent neural tube defects in early pregnancy. Supplements use folic acid or methylfolate, which count for more than food folate.
Calculator Official intake Study doses Best form Works with Safety Sources
PRI (population reference intake)
| Men | 330 µg |
|---|---|
| Women | 330 µg |
| Pregnancy | 600 µg |
| Breastfeeding | 500 µg |
Safe upper limit: 1,000 µg a day
Safe limit is for folic acid and methylfolate from supplements and fortified foods, counted as plain µg (not DFE).
RDA (recommended dietary allowance)
| Men | 400 µg |
|---|---|
| Women | 400 µg |
| Pregnancy | 600 µg |
| Breastfeeding | 500 µg |
Safe upper limit: 1,000 µg a day
Safe limit is for synthetic folic acid, counted as plain µg (not DFE).
NIH advises women who could become pregnant to take 400 µg folic acid a day from supplements or fortified food.
Source: National Academies (NASEM) 2019
Targets are in µg DFE (dietary folate equivalents). 1 µg folic acid taken with food counts as about 1.7 µg DFE.
These are doses tested in research, not personal advice. Some exceed the upper limit because they were short courses or given under medical care.
400 µg a day
Official US advice: 400 µg folic acid a day from supplements or fortified food for all women who could become pregnant, on top of food folate.
4,000 µg a day
The MRC trial gave 4 mg folic acid a day around conception and cut recurrence by 72%. This is far above the safe limit and is a prescribed dose, not a self-care dose.
800 µg a day
CSPPT: 20,702 adults with high blood pressure in China took enalapril with or without 0.8 mg folic acid. Strokes were about 21% fewer with folic acid (2.7% vs 3.4%). China had no folic acid food fortification, so the effect may be smaller where flour is fortified.
Best form
Folic acid (µg on label)
Why: Folic acid is the form that prevented neural tube defects in the landmark trials and is used in food fortification.
Alternatives: Methylfolate (5-MTHF) is the active form and needs no conversion. In a 2026 trial in 110 pregnant women at equal molar doses it matched folic acid on red-cell folate and homocysteine, and left about half as much unmetabolised folic acid in the blood. Folic acid stays the pick because it is the form that prevented neural tube defects in the landmark trials, and it costs less.
MRC Vitamin Study Research Group 1991 · Ernawati E et al. 2026
Large amounts of folic acid can correct the anaemia of B12 deficiency but not the nerve damage, so a B12 problem can go unnoticed. If you take folic acid, make sure your B12 intake is adequate too.
For targets, PillMath converts folic acid to DFE (x1.7 EFSA, x1.67 NIH). For the safe limit it counts the plain µg.
Leafy greens, legumes, liver, citrus, fortified cereals.
High folic acid can mask B12 deficiency anaemia while nerve damage goes on. Methotrexate and some anti-seizure drugs interact.
The safe limit (1000 µg) is for folic acid and methylfolate from supplements and fortified food.
Pregnant, breastfeeding, on medication, or managing a health condition? Check with a doctor or pharmacist before starting a supplement.
Values checked: November 12, 2026.
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