Evidence-based·Last reviewed May 31, 2026·How we grade evidence

Vitamin B9 (5-Methyltetrahydrofolate)

Vitamin5-methyltetrahydrofolate

The active coenzyme form of folate that skips the MTHFR conversion step folic acid requires. It's clearly preferred for people with MTHFR variants who don't tolerate folic acid, but for the general public the evidence that 5-MTHF beats folic acid for any clinical outcome — including in MTHFR carriers — is much thinner than the marketing suggests.

Quick decision guide

May help most

People with documented MTHFR C677T variants who don't respond well to folic acid, depression patients on SSRIs who haven't responded fully, and anyone whose clinician specifically recommends the active form.

Common dosing range

400–800 mcg/day for general folate replacement; 7.5–15 mg/day in psychiatry as an SSRI adjunct.

When to expect effects

Weeks for red-cell folate to rise; ≥6 weeks before judging depression-adjunct effect.

Watch out for

Costs 3–10× more than folic acid for no proven outcome benefit in most people. For pregnancy NTD prevention the CDC still recommends folic acid — not 5-MTHF — even for MTHFR carriers.

Evidence snapshot

Raising blood folateStrong

Depression (SSRI adjunct)Emerging

NTD prevention in pregnancyLow

Outcome benefit over folic acidLow

What is it

5-Methyltetrahydrofolate (5-MTHF), also called methylfolate or L-methylfolate, is the biologically active form of vitamin B9 that circulates in blood and crosses cell membranes. It does not require enzymatic conversion before use.

Is it worth it for you?

Use this as a quick fit check, not a diagnosis.

Worth considering if…

You have a documented homozygous MTHFR C677T variant and your clinician prefers the bypass form

You're on an SSRI with partial response and your psychiatrist suggests L-methylfolate as an adjunct

You tolerate folic acid poorly or have a strong preference for the active form

You're already taking folic acid and want to switch on your clinician's advice (pregnancy excluded — see below)

Probably skip if…

You're trying to prevent neural tube defects in pregnancy — the CDC and ACOG still recommend folic acid (400–800 mcg/day) even in MTHFR carriers; the prevention data is on folic acid

You're a healthy adult with no MTHFR variant and no folate deficiency — generic folic acid does the job for a fraction of the price

You're hoping it will cure low energy, brain fog, or fatigue without other evidence of folate deficiency

Your supplement contains 5-MTHF only to charge a premium — check the elemental folate dose and DFE on the label

Evidence at a glance

Goal	Effect	Best fit	Time
Raising red-cell and serum folate Strong Evidence	Equivalent or modestly greater rise in serum and RBC folate vs equimolar folic acid; effect amplified in homozygous MTHFR C677T carriers	MTHFR variant carriers (especially homozygous C677T) and anyone who needs reliable folate-status correction	2–8 weeks to reach steady-state serum folate; longer for RBC folate
Adjunct to SSRIs for major depression Good Evidence	Roughly doubled response rate when added to SSRIs at 15 mg/day in SSRI-resistant MDD; no effect at 7.5 mg/day	Adults with major depressive disorder who have had a partial response to an SSRI, particularly those with low folate status or MTHFR variants	≥6 weeks of adjunctive treatment in the published trials
Pregnancy outcomes in MTHFR carriers Mixed Evidence	No demonstrated outcome advantage over folic acid for miscarriage or NTD prevention	Women who genuinely cannot tolerate folic acid and need an alternative — discuss with obstetrician	Not established for clinical pregnancy outcomes
Avoiding unmetabolized folic acid (UMFA) Mixed Evidence	5-MTHF generates essentially no UMFA; clinical-outcome translation unproven	Cautious users at high cumulative folic-acid intakes from supplements plus fortified foods who want to minimize UMFA exposure	UMFA differences are immediate; clinical significance not established

Raising red-cell and serum folate

Strong Evidence

Effect: Equivalent or modestly greater rise in serum and RBC folate vs equimolar folic acid; effect amplified in homozygous MTHFR C677T carriers
Best fit: MTHFR variant carriers (especially homozygous C677T) and anyone who needs reliable folate-status correction
Time: 2–8 weeks to reach steady-state serum folate; longer for RBC folate

Adjunct to SSRIs for major depression

Good Evidence

Effect: Roughly doubled response rate when added to SSRIs at 15 mg/day in SSRI-resistant MDD; no effect at 7.5 mg/day
Best fit: Adults with major depressive disorder who have had a partial response to an SSRI, particularly those with low folate status or MTHFR variants
Time: ≥6 weeks of adjunctive treatment in the published trials

Pregnancy outcomes in MTHFR carriers

Mixed Evidence

Effect: No demonstrated outcome advantage over folic acid for miscarriage or NTD prevention
Best fit: Women who genuinely cannot tolerate folic acid and need an alternative — discuss with obstetrician
Time: Not established for clinical pregnancy outcomes

Avoiding unmetabolized folic acid (UMFA)

Mixed Evidence

Effect: 5-MTHF generates essentially no UMFA; clinical-outcome translation unproven
Best fit: Cautious users at high cumulative folic-acid intakes from supplements plus fortified foods who want to minimize UMFA exposure
Time: UMFA differences are immediate; clinical significance not established

Evidence for 4 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Raising red-cell and serum folate

Strong Evidence

5-MTHF reliably raises blood folate at least as well as folic acid, gram-for-gram, in most people. In MTHFR variant carriers it may produce a larger or faster rise because it bypasses the reduced-function MTHFR enzyme. The NIH ODS notes that the bioavailability of 5-MTHF is 'the same as or greater than that of folic acid.' What's missing is clinical-outcome data showing this biomarker difference translates into fewer NTDs, better cognition, or improved pregnancy outcomes versus folic acid.

Effect size

Equivalent or modestly greater rise in serum and RBC folate vs equimolar folic acid; effect amplified in homozygous MTHFR C677T carriers

Time to effect

2–8 weeks to reach steady-state serum folate; longer for RBC folate

Best fit

MTHFR variant carriers (especially homozygous C677T) and anyone who needs reliable folate-status correction

Less likely

Healthy adults with normal folate status — folic acid is equally effective for raising blood levels in most people

Bottom line: Reliable at raising blood folate. Whether that biomarker advantage matters clinically is the open question.

SourceNIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS ClinicalTrials.gov NCT06935630 — 5-MTHF vs folic acid in pregnant women — ClinicalTrials.gov

Adjunct to SSRIs for major depression

Disease adjunct

Good Evidence

The strongest condition-specific evidence for 5-MTHF is as an add-on to SSRIs in patients with partial or no response. In Papakostas et al. 2012 (PMID 23212058), 15 mg/day of L-methylfolate added to an SSRI in SSRI-resistant major depressive disorder produced a 32.3% response rate vs 14.6% for placebo (p=0.04). A lower 7.5 mg/day dose was no better than placebo. The effect is modest and limited to a specific clinical context — partial SSRI response, not first-line monotherapy.

Effect size

Roughly doubled response rate when added to SSRIs at 15 mg/day in SSRI-resistant MDD; no effect at 7.5 mg/day

Time to effect

≥6 weeks of adjunctive treatment in the published trials

Best fit

Adults with major depressive disorder who have had a partial response to an SSRI, particularly those with low folate status or MTHFR variants

Less likely

First-line monotherapy for depression; SSRI-naive patients; subclinical low mood without diagnosed MDD

Bottom line: Reasonable specialist-supervised add-on for SSRI-resistant depression at 15 mg/day. Not a primary antidepressant and not an over-the-counter mood booster.

Evidence is mixed

Effect was statistically significant only at 15 mg/day, not 7.5 mg/day, and most positive trials come from the same research group with industry funding. Independent replication is limited.

SourcePapakostas et al., 2012 — L-methylfolate adjunct for SSRI-resistant depression — PubMed — Am J Psychiatry· conflicting

SourcePapakostas et al., 2012 — L-methylfolate adjunct for SSRI-resistant depression — PubMed — Am J Psychiatry

Pregnancy outcomes in MTHFR carriers

Mixed Evidence

Despite heavy marketing, head-to-head 5-MTHF vs folic acid trials in pregnancy haven't shown an outcome advantage. Cirillo et al. 2016 (PMC4668025) randomized women with recurrent miscarriage stratified by MTHFR C677T and A1298C status to 5-MTHF or folic acid; results 'did not support any beneficial effect of 5-MTHF vs. folic acid supplementation.' Critically, ALL the high-quality NTD-prevention data — including the Wald and Czeizel trials — used folic acid. The CDC and ACOG still recommend 400–800 mcg folic acid for pregnancy NTD prevention, even in MTHFR variant carriers.

Effect size

No demonstrated outcome advantage over folic acid for miscarriage or NTD prevention

Time to effect

Not established for clinical pregnancy outcomes

Best fit

Women who genuinely cannot tolerate folic acid and need an alternative — discuss with obstetrician

Less likely

Anyone choosing 5-MTHF over folic acid for routine preconception/pregnancy NTD prevention based on marketing claims

Bottom line: Stick with folic acid for pregnancy NTD prevention unless your obstetrician has a specific reason to switch. The case for 5-MTHF here is mechanism-only.

Evidence is mixed

NTD-prevention trials all used folic acid. Switching pregnant patients to 5-MTHF means extrapolating from biomarker data, not outcome data. Current trials (NCT06935630 and others) are measuring RBC folate, not NTD or pregnancy-loss endpoints.

SourceCirillo et al., 2016 — PMC — Methyltetrahydrofolate vs Folic Acid in Idiopathic Recurrent Miscarriage RCT· conflicting ClinicalTrials.gov NCT06935630 — 5-MTHF vs folic acid in pregnant women — ClinicalTrials.gov Georgetown Medical Review — Proposed shift from folic acid to 5-MTHF — Georgetown Medical Review

SourceCirillo et al., 2016 — PMC — Methyltetrahydrofolate vs Folic Acid in Idiopathic Recurrent Miscarriage RCT NIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS MGH Center for Women's Mental Health — L-methylfolate in pregnancy — MGH Center for Women's Mental Health

Avoiding unmetabolized folic acid (UMFA)

Mechanism only

Mixed Evidence

A popular theoretical argument for 5-MTHF is that it avoids unmetabolized folic acid (UMFA) — folic acid that enters circulation before being reduced to active forms. UMFA at high doses has been linked in observational data to reduced natural killer cell activity and cognitive concerns in older adults. However, the clinical relevance is unproven: no RCT has shown that switching from folic acid to 5-MTHF reduces meaningful clinical events. UMFA appears mostly at single doses ≥300–400 mcg, so spacing or splitting doses also addresses it.

Effect size

5-MTHF generates essentially no UMFA; clinical-outcome translation unproven

Time to effect

UMFA differences are immediate; clinical significance not established

Best fit

Cautious users at high cumulative folic-acid intakes from supplements plus fortified foods who want to minimize UMFA exposure

Less likely

Users at typical 400 mcg/day folate intakes from standard prenatal or multivitamins

Bottom line: The UMFA argument is biologically reasonable but lacks outcome data. Most people don't need to chase it.

SourceNIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS Georgetown Medical Review — Proposed shift from folic acid to 5-MTHF — Georgetown Medical Review

How it works

5-MTHF serves as a methyl donor in the conversion of homocysteine to methionine, supporting DNA synthesis, neurotransmitter production, and the body's methylation reactions overall. Other B9 forms (folate from food, folic acid from supplements) must be converted through several enzymatic steps — including via the MTHFR enzyme — to become 5-MTHF. People with common MTHFR genetic variants (C677T, A1298C) have reduced conversion capacity. For them, supplementing with the already-converted 5-MTHF form theoretically bypasses the bottleneck. Whether this translates to better clinical outcomes for most people is debated.

How to take it

1. Typical dose

• 400–800 mcg/day (DFE-equivalent) for general folate adequacy • 1 mg/day for therapeutic replacement in confirmed deficiency or MTHFR carrier protocols • 7.5–15 mg/day under psychiatrist supervision as an SSRI adjunct (15 mg is the dose with positive RCT data)

2. Higher studied dose

15 mg/day in adjunctive depression trials. Higher doses are unstudied for the general public; the 1,000 mcg/day UL for synthetic folate (set for folic acid) is typically extrapolated to 5-MTHF in non-psychiatric use.

3. Timing

Take with or without food. Light- and heat-sensitive — keep capsules in their original opaque bottle, not a clear pill organizer in direct light.

4. With food

Either is fine.

5. Split dosing

Single daily dose at standard intakes (400–800 mcg). Psychiatric doses of 15 mg/day are typically given as a single morning dose.

6. How long to try

Allow 8 weeks to assess blood-folate or mood response. For SSRI-augmentation, give ≥6 weeks at 15 mg/day before judging.

What to track

Serum or RBC folate level if a clinician is monitoring deficiency

Mood symptoms (e.g., PHQ-9) if using as an SSRI adjunct

Energy and any GI side effects

Vitamin B12 level — high folate can mask B12 deficiency anemia; check B12 BEFORE starting high-dose folate of any form

Bottom line: 400–800 mcg/day covers general adequacy. Don't pay a premium for 5-MTHF unless you have a documented MTHFR variant or your clinician specifically recommends it. For pregnancy NTD prevention, default to folic acid.

5 commercial forms

Compare the main delivery options and what they’re best suited for.

L-5-MTHF calcium salt (Metafolin)

Most-studied 5-MTHF form

The original patented stable form of L-5-MTHF, used in most of the clinical research including the Papakostas depression trial. Crystalline, light-sensitive, and the form referenced when studies say '5-MTHF.'

Reference form for the published 5-MTHF research.

Quatrefolic (glucosamine salt of L-5-MTHF)

Newer, higher solubility

Glucosamine salt designed for improved solubility and stability over the calcium salt. Common in newer prenatals and B-complexes. Bioavailability data is largely manufacturer-supplied; comparative head-to-head trials with Metafolin are limited.

Likely similar to Metafolin; less independent clinical data.

Folic acid (pteroylmonoglutamic acid)

Standard / most evidence

The synthetic folate used in food fortification, prenatals, and virtually all the major NTD-prevention and clinical-outcome trials. Requires DHFR and MTHFR enzymes to convert to active 5-MTHF — a slow pathway in MTHFR variant carriers. Far cheaper than 5-MTHF.

≥85% bioavailable with food; conversion limited in MTHFR variants.

Folinic acid (5-formyltetrahydrofolate, leucovorin)

Intermediate / clinical use

A reduced folate that bypasses DHFR but still requires MTHFR. Mostly used in clinical settings as 'leucovorin rescue' after methotrexate. Some practitioners prefer it over 5-MTHF for individuals who report agitation on L-methylfolate.

Well absorbed; bypasses DHFR but not MTHFR.

Food folate (5-MTHF and polyglutamates from leafy greens, legumes)

Whole-food source

Naturally occurring folates in food are largely 5-MTHF polyglutamates, deconjugated and absorbed similarly to supplemental 5-MTHF. About 50% bioavailability vs supplements due to food-matrix effects.

≈50% bioavailable; counts as DFE on labels.

Safety

Know the common side effects, key cautions, and who should avoid it.

Common side effects

mild GI upset (uncommon)insomnia or vivid dreams at higher psychiatric dosesirritability or anxiety at higher psychiatric doses

Serious risks

Masking vitamin B12 deficiency — any high-dose folate (folic acid OR 5-MTHF) can correct the anemia of B12 deficiency while neurological damage progresses unchecked. Always check B12 before starting ≥1 mg/day folate of any form.
SourceNIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS
Psychiatric activation at higher doses (15 mg+) — some people report agitation, insomnia, or anxiety, especially with rapid dose escalation. Start lower and titrate up under clinician guidance.
SourcePapakostas et al., 2012 — L-methylfolate adjunct for SSRI-resistant depression — PubMed — Am J Psychiatry

Who should avoid it

People with a history of folate-responsive seizure disorders without neurology guidance — high-dose folate can alter anticonvulsant levels.
SourceNIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS
Patients on methotrexate for cancer — discuss with oncology before any folate supplementation, as it can interfere with the drug's anticancer effect.
SourceNIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS
Anyone with undiagnosed megaloblastic anemia until B12 deficiency is ruled out.
SourceNIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS

Pregnancy & breastfeeding

Pregnancy RDA is 600 mcg DFE/day. The CDC and ACOG still recommend 400–800 mcg/day of folic acid (not 5-MTHF) for NTD prevention, even in MTHFR variant carriers, because all the NTD-prevention trials used folic acid. The L-methylfolate safety database in pregnancy is much smaller. If you're already taking 5-MTHF and want to continue in pregnancy, discuss with your obstetrician — many keep prenatal folic acid in place and add 5-MTHF as a separate adjunct rather than swap.

SourceNIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS MGH Center for Women's Mental Health — L-methylfolate in pregnancy — MGH Center for Women's Mental Health Cirillo et al., 2016 — PMC — Methyltetrahydrofolate vs Folic Acid in Idiopathic Recurrent Miscarriage RCT

Bottom line: Safer than the marketing makes folic acid sound, but not safer than folic acid itself for established uses. Check B12 before any high-dose folate. For pregnancy, default to folic acid unless your OB advises otherwise.

Interactions

methotrexate (for cancer)Major

Folate of any form may reduce methotrexate's anticancer effect. Always coordinate with oncology before starting; low-dose folate is sometimes given intentionally to reduce methotrexate toxicity in rheumatology, but cancer dosing is different.

SourceNIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS

anticonvulsants (phenytoin, carbamazepine, valproate, phenobarbital)Moderate

These drugs lower serum folate; folate supplements can in turn reduce serum levels of the anticonvulsants. Have folate and drug levels monitored if both are needed long-term.

SourceNIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS

sulfasalazineModerate

Sulfasalazine blocks intestinal folate absorption and can cause functional folate deficiency; supplementation is often needed but should be separated by 2+ hours from the dose.

SourceNIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS

trimethoprim and pyrimethamineModerate

These antifolate drugs inhibit dihydrofolate reductase; folate supplementation may reduce their antimicrobial effect. Coordinate with prescriber.

SourceNIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS

Food sources

Food	Amount	%DV
Beef liver, cooked	3 oz (215 mcg DFE)	54%
Spinach, boiled	½ cup (131 mcg DFE)	33%
Black-eyed peas, boiled	½ cup (105 mcg DFE)	26%
Breakfast cereals, fortified	1 serving (100 mcg DFE)	25%
Rice, white, enriched, cooked	½ cup (90 mcg DFE)	23%
Asparagus, boiled	4 spears (89 mcg DFE)	22%
Spaghetti, cooked, enriched	½ cup (83 mcg DFE)	21%
Brussels sprouts, frozen, boiled	½ cup (78 mcg DFE)	20%
Lettuce, romaine, shredded	1 cup (64 mcg DFE)	16%
Avocado, raw, sliced	½ cup (59 mcg DFE)	15%
Broccoli, chopped, frozen, cooked	½ cup (52 mcg DFE)	13%
Egg, hard-boiled	1 large (22 mcg DFE)	6%

Beef liver, cooked

Amount: 3 oz (215 mcg DFE)
%DV: 54%

Spinach, boiled

Amount: ½ cup (131 mcg DFE)
%DV: 33%

Black-eyed peas, boiled

Amount: ½ cup (105 mcg DFE)
%DV: 26%

Breakfast cereals, fortified

Amount: 1 serving (100 mcg DFE)
%DV: 25%

Rice, white, enriched, cooked

Amount: ½ cup (90 mcg DFE)
%DV: 23%

Asparagus, boiled

Amount: 4 spears (89 mcg DFE)
%DV: 22%

Spaghetti, cooked, enriched

Amount: ½ cup (83 mcg DFE)
%DV: 21%

Brussels sprouts, frozen, boiled

Amount: ½ cup (78 mcg DFE)
%DV: 20%

Lettuce, romaine, shredded

Amount: 1 cup (64 mcg DFE)
%DV: 16%

Avocado, raw, sliced

Amount: ½ cup (59 mcg DFE)
%DV: 15%

Broccoli, chopped, frozen, cooked

Amount: ½ cup (52 mcg DFE)
%DV: 13%

Egg, hard-boiled

Amount: 1 large (22 mcg DFE)
%DV: 6%

Choosing a product

What to look for on the label — and what to be skeptical of.

Look for…

Look for 'L-5-MTHF', '(6S)-5-methyltetrahydrofolate', 'Metafolin', or 'Quatrefolic' on the label — those are the well-characterized chiral-active forms

Elemental folate dose stated in mcg DFE (dietary folate equivalents) — not just the weight of the calcium or glucosamine salt

Third-party tested (USP, NSF, ConsumerLab) — confirms the active stereoisomer content

Opaque packaging (amber or opaque bottle) — 5-MTHF is light-sensitive and degrades in clear containers

Paired with B12 (methylcobalamin or hydroxocobalamin) if you're not sure of your B12 status, to avoid masking deficiency

Be skeptical of…

Claims that 5-MTHF prevents neural tube defects 'better than' folic acid — the NTD evidence is on folic acid, not 5-MTHF

MTHFR-test marketing that pushes expensive 5-MTHF on anyone with any MTHFR variant — only homozygous C677T meaningfully reduces folate metabolism, and the CDC still recommends folic acid even then

'Detox' or 'methylation support' bundles combining 5-MTHF with TMG/SAMe/B12 at premium prices without evidence the combination outperforms a basic B-complex

Mega-dose products (15 mg) marketed for general wellness — 15 mg is the studied dose for SSRI-resistant depression under psychiatric supervision, not for daily over-the-counter use

Frequently asked questions

Should I take methylfolate instead of folic acid?⌄

If you have a known MTHFR variant or prefer to avoid unmetabolized folic acid, methylfolate is a reasonable choice. For most people without those concerns, folic acid works fine and is cheaper.

Is methylfolate better for pregnancy?⌄

It likely provides similar protection against neural tube defects, but folic acid has the longest track record and is what most guidelines specifically recommend.

Can methylfolate help depression?⌄

Prescription L-methylfolate at higher doses (7.5 to 15 mg) has shown modest benefit as an antidepressant adjunct in some trials, especially for people with folate deficiency or MTHFR variants.

How much methylfolate should I take?⌄

For general supplementation, 400 to 1,000 mcg per day. Higher prescription doses are used for specific medical indications under physician guidance.

Do I need to take methylfolate if I have MTHFR variants?⌄

Many providers recommend it, but the clinical importance of common MTHFR variants in otherwise healthy people is debated. It is a reasonable choice but not strictly necessary for everyone.

References by claim

Raising red-cell and serum folate

NIH Office of Dietary Supplements — Folate (Health Professional) — NIH ODS (2024) link

ClinicalTrials.gov NCT06935630 — 5-MTHF vs folic acid in pregnant women — ClinicalTrials.gov (2025) link

Pregnancy outcomes in MTHFR carriers

Cirillo et al., 2016 — PMC — Methyltetrahydrofolate vs Folic Acid in Idiopathic Recurrent Miscarriage RCT (2016) link

MGH Center for Women's Mental Health — L-methylfolate in pregnancy — MGH Center for Women's Mental Health (2024) link

Georgetown Medical Review — Proposed shift from folic acid to 5-MTHF — Georgetown Medical Review (2024) link

Adjunct to SSRIs for major depression

Papakostas et al., 2012 — L-methylfolate adjunct for SSRI-resistant depression — PubMed — Am J Psychiatry (2012) link

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Evidence-based·Last reviewed May 31, 2026·Evidence current as of May 31, 2026·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.