Vitamin B9 / Folate

Best for

Lower neural tube defect risk

Proven strong benefit · 0.36–4 mg/day for 12–16 weeks · 1 meta-analysis , n=6.8k

52 papers · 6 claims · 76 outcomes scored · 4 positive

Outcomes

What vitamin b9 / folate actually does, by outcome

Each row is one outcome with effect size, evidence base, the dose that worked in trials, and time to first effect. Magnitude tiers come from native-unit MCID where available, Cohen's d otherwise.

Outcome Effect size Evidence Dose Weeks Rank

Lower neural tube defect risk Proven strong benefit

Fuels the rapid cell division that seals the spine before week four.

3 meta-analyses n=6.8k 0.36–4 mg 12–16 wk

1489222·26662928·6786536

large

3 meta-analyses n=6.8k Meta-analyzed

0.36–4 mg

12–16 wk

—

Lower homocysteine levels Proven benefit

Clears a vessel-irritating byproduct that builds when nutrient recycling falls behind.

19 meta-analyses n=3.2k 0.25–2000 mcg 4–52 wk #1/12

16871332·20216560·20847105·22230384 +15 more

moderate

19 meta-analyses n=3.2k Meta-analyzed I²=84%

0.25–2000 mcg

4–52 wk

#1 /12

Build nutrient stores in pregnancy Likely benefit

Tops up the reserves pregnancy drains fastest.

21 meta-analyses n=2.6k 0–1429 mcg 4–52 wk #1/4

16871332·22254076·23456769·23543547 +17 more

moderate

21 meta-analyses n=2.6k Meta-analyzed I²=97%

0–1429 mcg

4–52 wk

#1 /4

Lower your blood pressure Likely real but unnoticeable

Brings down both systolic and diastolic, especially when baseline runs high.

3 RCTs n=367 0.4–5 mg 6–24 wk #10/81

25748442·35060542·37433173

trivial

3 RCTs n=367

0.4–5 mg

6–24 wk

#10 /81

Lower congenital heart defect risk Not enough research

May help support normal heart formation in early pregnancy.

1 meta-analysis n=107k — —

35346212

—

1 meta-analysis n=107k Meta-analyzed I²=96%

—

Lower preterm birth risk Not enough research

Reduces the chance of early delivery, especially before 34 weeks.

2 meta-analyses n=2.3k 0.25–5 mg —

22992251·30209050

—

2 meta-analyses n=2.3k Meta-analyzed

0.25–5 mg

—

Outcome	Effect	Evidence	Dose	Weeks	Rank
Lower neural tube defect risk Proven strong benefit	large	3 meta-analyses n=6.8k Meta-analyzed	0.36–4 mg	12–16 wk	—
Lower homocysteine levels Proven benefit	moderate	19 meta-analyses n=3.2k Meta-analyzed	0.25–2000 mcg	4–52 wk	#1/12
Build nutrient stores in pregnancy Likely benefit	moderate	21 meta-analyses n=2.6k Meta-analyzed	0–1429 mcg	4–52 wk	#1/4
Lower your blood pressure Likely real but unnoticeable	trivial	3 RCTs n=367	0.4–5 mg	6–24 wk	#10/81
Lower congenital heart defect risk Not enough research		1 meta-analysis n=107k Meta-analyzed	—	—	—
Lower preterm birth risk Not enough research		2 meta-analyses n=2.3k Meta-analyzed	0.25–5 mg	—	—

Buy well

Recommended Vitamin B9 / Folate products

Real products that dose Vitamin B9 / Folate where the research does, in a clean formulation, from brands we've audited. We only list ones we'd stand behind.

Chosen for adequate Vitamin B9 / Folate dosing vs. the studied range, a clean formulation (grade A–C), and independent brand-quality audits. Not sponsored.

Risk profile

Adverse events and known drug interactions

Safety events

severe vertigo severe

abdominal cramps; severe vertigo; bilateral hydronephrosis severe

seizure severe

hypertension moderate

pregnancy moderate

gastrointestinal discomfort (poor digestion / abdominal bloating) moderate

headache mild

abdominal cramps

Drug interactions

Phenytoin major decreases concentration

Carbamazepine major decreases concentration

Phenobarbital major decreases concentration

Primidone moderate decreases concentration

Primidone moderate decreases effect

Aspirin moderate decreases concentration

Metformin minor decreases concentration

Warfarin minor decreases concentration

Co-studied with

Supplements that share evidence with vitamin b9 / folate

Sources

Generated August 14, 2026

Vitamin B9 / Folate

What vitamin b9 / folate actually does, by outcome

Recommended Vitamin B9 / Folate products

Adverse events and known drug interactions

Supplements that share evidence with vitamin b9 / folate

More evidence for Vitamin B9 / Folate

From Leaves to Lifelines: How a Quiet Vitamin Rewrote Birth—and Keeps Surprising Us

Best Supplements to Clear Old Clots More Efficiently (2026)

Garlic

L-Methionine

Vitamin B12

Vitamin B2

Vitamin B9 / Folate

Recommended Vitamin B9 / Folate products

More evidence for Vitamin B9 / Folate

NewFrom Leaves to Lifelines: How a Quiet Vitamin Rewrote Birth—and Keeps Surprising Us

NewBest Supplements to Clear Old Clots More Efficiently (2026)

NewGarlic

NewL-Methionine

NewVitamin B12

NewVitamin B2

From Leaves to Lifelines: How a Quiet Vitamin Rewrote Birth—and Keeps Surprising Us

Best Supplements to Clear Old Clots More Efficiently (2026)

Garlic

L-Methionine

Vitamin B12

Vitamin B2