Clear evidence. Transparent sources. Practical guidance. Our evidence policyContact
Food Health Lab
Home › Supplements › B9 · Folate

Vitamin B9 (Folate) — The Complete Supplement Guide

The pregnancy vitamin: folic acid before conception prevents neural-tube defects. Folate vs folic acid vs methylfolate, doses and the B12 caveat.

Reviewed by Bodil Isaksson, Licensed Biomedical Scientist (Sweden)Last reviewed July 2026Supplement guide

SupplementsVitaminsB9 FolateWater-soluble

Needs rise sharply whenever the body is building new cells fastest — above all in early pregnancy, which is why it’s the one supplement widely advised before conception. For the short dietary version, see the Vitamins page.

Read first. Folic acid before and in early pregnancy prevents serious birth defects — but high folic acid can mask a vitamin B12 deficiency, delaying its diagnosis. Check B12 status too, especially in vegans and older adults. Information, not a prescription.

Key takeaways

  • Take 400 µg/day folic acid before and in early pregnancy to cut the risk of neural-tube defects.
  • Adults need ≈ 330–400 µg DFE/day (600 in pregnancy).
  • Upper limit 1,000 µg/day from folic acid.

Function

Folate is essential wherever cells divide:

  • DNA synthesis & cell division: needed to build DNA and make new cells — critical in growth and pregnancy.
  • Red blood cells: deficiency causes large, immature red cells (megaloblastic anaemia).
  • Neural-tube development: vital in the first weeks of pregnancy to close the baby's spine and brain.
  • Homocysteine: with B12 and B6, converts homocysteine to methionine.
  • Methylation: supplies methyl groups for DNA and neurotransmitter reactions.

Different forms — and which to choose

FolateThe natural form in food.
Folic acidThe stable synthetic form in supplements and fortification — best-absorbed and the form proven to prevent neural-tube defects.
L-methylfolate (5-MTHF)The active form; an option for people with MTHFR variants or who prefer a pre-activated folate.

Absorption in the body

How muchFolic acid ~85% absorbed vs food folate ~50% — hence the pregnancy advice specifies folic acid.
NoteIntake is given as "dietary folate equivalents" (DFE) to account for this difference.

Deficiency symptoms

SymptomsMegaloblastic anaemia, fatigue and mouth sores; in early pregnancy, raised risk of neural-tube defects.
Who's at riskPregnancy, poor diets, malabsorption (coeliac), heavy alcohol use, and some medications (methotrexate).

Recommended intake

Adults ≈ 330–400 µg DFE · Pregnancy 600

Reference intakes:

  • Adults: ~330–400 µg DFE/day · Pregnancy: ~600 µg DFE/day

Best sources: dark leafy greens, legumes, beetroot, citrus and fortified grains.12

Therapeutic use

Pregnancy400 µg/day folic acid before conception and through the first trimester to prevent neural-tube defects; 4–5 mg (prescription) for higher-risk pregnancies.
AnaemiaTreating folate-deficiency anaemia.

Therapeutic doses

Pre-pregnancy: 400 µg/day folic acid
EverydayA varied diet plus fortified foods usually suffices.
Check B12 firstBefore high-dose folate, especially in vegans/older adults, confirm B12 is adequate.

Toxicity & upper limit

UL: 1,000 µg/day folic acid
Upper limit1,000 µg/day of folic acid (the synthetic form; food folate is not limited).1
Masks B12High folic acid can correct the anaemia of B12 deficiency while nerve damage silently progresses.

Bottom line: everyone who could become pregnant should take 400 µg/day folic acid — it prevents serious birth defects. Otherwise eat your greens and legumes, keep supplemental folic acid under 1,000 µg/day, and make sure your B12 is covered.

← All supplementsShort dietary version

References

Reference and upper-limit values are general adult figures from official bodies; individual needs vary. Therapeutic doses describe clinical/research use, not prescriptions.

  1. US NIH Office of Dietary Supplements. Folate — Health Professional Fact Sheet (function, forms, intakes, food sources, deficiency, therapeutic uses, upper limit, interactions). ods.od.nih.gov
  2. EFSA. Dietary Reference Values & Tolerable Upper Intake Levels for vitamins (European reference intakes and ULs). efsa.europa.eu

This article summarizes nutrition science from official health authorities and peer-reviewed sources for education. It is not a substitute for individual medical advice, and the doses given are not prescriptions — always consult a professional before therapeutic supplement use, in pregnancy, or alongside medication.

✓
Bodil Isaksson, Licensed Biomedical Scientist (Sweden)

At Food Health Lab we explain what the science says in plain language, and we cite our sources so you can check for yourself.

Read next

Vitamin
Vitamin B12
Vitamin
Vitamin A
Vitamin
Vitamin D