Vitamin B9 (Folic Acid): Dosage, Timing & Interactions

Check it against something

Evidence level A

Vitamin B9 (Folic Acid) with:

99 out of 100

Works better together Take together — same timing window amplifies the synergy.

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What it does

mechanism and evidence for each claim

Neural tube defect prevention

Reduces risk of spina bifida and anencephaly by 50-70%

Provides folate for neural tube closure after conversion Evidence A-grade Must be adequate before conception

DNA synthesis support

Essential for proper cell division and DNA integrity

Converted to active forms for nucleotide synthesis Evidence A-grade Ongoing cellular process

Anemia prevention

Prevents megaloblastic anemia

Required for DNA synthesis in red blood cell formation Evidence A-grade 4-8 weeks

Cardiovascular health

Helps maintain healthy homocysteine levels

Converted to methylfolate for homocysteine metabolism Evidence A-grade 4-8 weeks

Cost-effective supplementation

Most affordable way to increase folate status

Synthetic form is less expensive to manufacture Evidence A-grade Immediate economic benefit

Or a different form of the same thing

the comparison people search most

Vitamin B9 (Folic Acid) vs Folate (5-MTHF) absorption 85 against 95 · $5 against $20 a month 95% Vitamin B9 (Folic Acid) vs Vitamin B9 (Folinic Acid) absorption 85 against 98 · $5 against $100 a month 98%

All Folate forms ranked by absorption →

Every pair we checked

12 combinations scored by the engine

Vitamin B9 (Folic Acid) + Caffeine No documented interaction either way No known interaction 70

Vitamin B9 (Folic Acid) + Creatine Monohydrate No documented interaction either way No known interaction 70

Vitamin B9 (Folic Acid) + Whey Protein No documented interaction either way No known interaction 70

Vitamin B9 (Folic Acid) + Turmeric No documented interaction either way No known interaction 70

Vitamin B9 (Folic Acid) + Zinc Gluconate Zinc deficiency impairs folate utilization Needs attention 76

Vitamin B9 (Folic Acid) + Lactase Improved calcium absorption when consuming dairy Works better together 82

Vitamin B9 (Folic Acid) + Bovine Collagen Essential for collagen synthesis and cross-linking Works better together 82

Vitamin B9 (Folic Acid) + DHA Prevents oxidation of DHA and enhances stability Works better together 82

Vitamin B9 (Folic Acid) + Calcium Carbonate Essential for calcium absorption and utilization Works better together 94

Vitamin B9 (Folic Acid) + Vitamin D3 Work together in methylation and DNA synthesis Works better together 99

Vitamin B9 (Folic Acid) + Vitamin C (Ascorbic Acid) Work together in methylation and DNA synthesis Works better together 99

Vitamin B9 (Folic Acid) + Vitamin B12 (Methylcobalamin) Work together in methylation and DNA synthesis Works better together 99

Dosage

Morning with food

Daily400-800 mcg

Maintenance400-600 mcg

Therapeutic800-1000 mcg

Maximum1000 mcg (tolerable upper limit)

Pregnancy400-800 mcg

Upper limit 1000 mcg NIH ODS

Before you take it

Pregnancyrecommended

VeganYes

When to expect it

First Effects2-4 weeks for cellular processes

Peak Benefits8-12 weeks for cardiovascular and hematological benefits

Deficiency Development4-12 weeks with inadequate intake

Toxicity OnsetNo acute toxicity, but concerns about chronic high intake

How to measure it

$40-80

MarkerSerum folate and RBC folate

OptimalSerum: >7 ng/mL, RBC: >140 ng/mL

Deficient belowSerum: <3 ng/mL, RBC: <140 ng/mL

FrequencyAnnually for pregnant women, as needed for others

What actually reaches you

The label counts the carrier, your body does not

Absorption Very high 85 of 100 · best absorbed form of this compound

Delivered daily 0.5 mg

Cost per 10 mg delivered $3.27 comparative — uses the absorption score, not a measured percentage

Works better with

3 documented

+

Vitamin B12

Work together in methylation and DNA synthesis

Complementary roles in one-carbon metabolism · level A

+

Vitamin B6

Both involved in homocysteine metabolism

Sequential steps in methylation pathway · level A

+

Vitamin C

Protects folate from oxidation

Antioxidant protection and folate regeneration · level B

What not to take with Vitamin B9 (Folic Acid)

3 documented

!

Alcohol

Significantly impairs folate absorption and metabolism

Interferes with folate transport and conversion · major significance

!

Zinc Deficiency

Zinc deficiency impairs folate utilization

Zinc required for folate-dependent enzymes · moderate significance

!

Sulfasalazine

Inhibits folate absorption

Structural similarity interferes with folate transport · moderate significance

Medication interactions

Discuss these with a pharmacist before combining

methotrexate Major

Folic acid may reduce methotrexate effectiveness

What to do: Avoid folic acid supplements during treatment

anticonvulsants Moderate

Some anticonvulsants deplete folate

What to do: Monitor folate status, consider supplementation

trimethoprim Moderate

Interferes with folate metabolism

What to do: May need folate supplementation

Available forms

bioavailability compared

Ranks 3 of 3 among folate forms. Vitamin B9 (Folinic Acid) absorbs better — 98%. Compare all forms →

Folic Acid 85

Folic Acid: Most research, Least expensive, Very stable, High absorption

Food sources

before you supplement

Fortified cereals 100-400 mcg/serving · 85

Enriched bread 43 mcg/slice · 85

Fortified pasta 110 mcg/cup · 85

Note: Folic acid is added to fortified foods Natural foods contain folate, not folic acid · 85

Too little

deficiency signs

Megaloblastic anemia
Fatigue and weakness
Irritability and depression
Poor memory and concentration
Glossitis (smooth, red tongue)
Neural tube defects in pregnancy
Elevated homocysteine levels

Too much

toxicity signs

No acute toxicity symptoms
Possible unmetabolized folic acid in blood
May mask B12 deficiency
Theoretical immune system effects
Upper limit of 1000 mcg established for safety

Who benefits most

pregnant-women-budget

Most cost-effective option for neural tube defect prevention

400-800 mcg daily

women-of-childbearing-age

Standard recommendation for all women who might become pregnant

400 mcg daily

cost-conscious-consumers

Most affordable folate supplementation option

400-800 mcg daily

general-population

Most widely available and studied form

400-600 mcg daily

elderly-basic-supplementation

Standard multivitamin component for basic needs

400-600 mcg daily

Where to buy it

compare forms first

Look for Vitamin B9 (Folic Acid) at 400-800 mcg per serving. The form that matters here is Folic Acid.

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What else affects it

Beyond other supplements

!

Alcohol

Significantly impairs folate absorption and metabolism

Interferes with folate transport and conversion

How it works

Absorbed in small intestine as monoglutamate
Converted to dihydrofolate, then tetrahydrofolate
Further converted to 5-methyltetrahydrofolate (active form)
Provides one-carbon units for DNA and RNA synthesis
Required for amino acid metabolism
Essential for purine and thymidine synthesis

Key findings

what the evidence supports

Prevents 50-70% of neural tube defects (NEJM 1992)
Most studied form of folate with decades of safety data
Effective for treating folate deficiency anemia
Fortification programs have virtually eliminated folate deficiency

Sources: NIH Examine.com · data reviewed 2026-08-01

Compiled by Denis, who maintains this database and holds no medical qualification — every figure here is sourced or derived, never asserted. How we calculate it →

Common questions

What are the benefits of Vitamin B9 (Folic Acid)?

Documented effects: Neural tube defect prevention; DNA synthesis support; Anemia prevention; Cardiovascular health. Reduces risk of spina bifida and anencephaly by 50-70%

How much Vitamin B9 (Folic Acid) should you take per day?

The common daily range is 400-800 mcg. By goal — maintenance: 400-600 mcg; therapeutic: 800-1000 mcg; maximum: 1000 mcg (tolerable upper limit); pregnancy: 400-800 mcg.

When is the best time to take Vitamin B9 (Folic Acid)?

Morning with food. First effects are typically reported within 2-4 weeks for cellular processes.

What are the side effects of Vitamin B9 (Folic Acid)?

At excessive doses: No acute toxicity symptoms, Possible unmetabolized folic acid in blood, May mask B12 deficiency, Theoretical immune system effects, Upper limit of 1000 mcg established for safety. Safety rating at normal doses is 8 out of 10.

What should you not take with Vitamin B9 (Folic Acid)?

Separate it from Alcohol, Zinc Deficiency, Sulfasalazine by two to four hours. Significantly impairs folate absorption and metabolism

Does Vitamin B9 (Folic Acid) interact with medications?

Documented interactions with methotrexate, anticonvulsants, trimethoprim. Discuss these with a pharmacist before combining.

How much Vitamin B9 (Folic Acid) is too much?

The tolerable upper intake level is 1000 mcg per day for adults, per NIH ODS. Above that, the risk of adverse effects rises: No acute toxicity symptoms, Possible unmetabolized folic acid in blood, May mask B12 deficiency.

How do you know if you need Vitamin B9 (Folic Acid)?

The marker is Serum folate and RBC folate, optimal range Serum: >7 ng/mL, RBC: >140 ng/mL. Common deficiency signs: Megaloblastic anemia, Fatigue and weakness, Irritability and depression, Poor memory and concentration.