Methylfolate (5-MTHF)
Best-in-class: 5-MTHF 1 mg
The active, bioavailable form of folate (vitamin B9) that bypasses the MTHFR conversion step, so it works even in the ~40% of people who methylate folic acid poorly.
Methylfolate (5-MTHF) quick facts
| Suggested dose | 1 mg daily (higher only under guidance). |
| How often | Daily |
| Who it's for | MTHFR variants, preconception/pregnancy, methylation and mood support. |
| Best-in-class brand | 5-MTHF 1 mg |
This is the form worth paying for, and it's one of the few places a genetic variant genuinely changes what you should buy. Two cautions. It must be run with adequate B12 — folate alone can normalize the blood picture of B12 deficiency while the neurological damage continues underneath, which is the classic way this goes wrong. And some people are notably sensitive to methyl donors and feel wired or irritable on a high dose; start low rather than assuming more is better.
How Methylfolate (5-MTHF) actually works
Folic acid is synthetic and inert until reduced twice, and the final step is done by methylenetetrahydrofolate reductase — the MTHFR enzyme. The common C677T variant reduces that enzyme's activity substantially, so folic acid can accumulate unconverted while the methylation cycle stays short of substrate. Methylfolate is the finished product and enters the cycle directly: it hands its methyl group to B12, which passes it to homocysteine to regenerate methionine and then SAMe, the body's universal methyl donor for DNA, myelin and neurotransmitters.
Where to get Methylfolate (5-MTHF)
Buy 5-MTHF 1 mg at Thorne →The evidence for Methylfolate (5-MTHF)
Graded by what exists behind each claim.
✅ Clinically validated
- Lowers homocysteine and raises red-cell folate more reliably than folic acid in MTHFR carriers (RCT-supported).
- Supports healthy neural-tube development in pregnancy and mood/methylation pathways.
📊 Correlative data
- Low folate status is associated with elevated homocysteine, mood disorders and cardiovascular risk.
🧪 Theoretical / extrapolated benefits
- Superiority of methylfolate over folic acid for outcomes beyond homocysteine is plausible but still being established.
How to read these tiers: they say how much human evidence exists, not how well something works — and ✗ flags harm, never a disappointing trial. How the evidence tiers work →
What Methylfolate (5-MTHF) actually does
5-methyltetrahydrofolate is not a better folate. It is the only folate that circulates. Whatever enters the body — food polyglutamates, synthetic folic acid, or 5-MTHF itself — the species in plasma and the species carried into cells by the reduced folate carrier and the folate receptor is 5-methyltetrahydrofolate. The difference between products is not the destination; it is how many enzymatic steps stand between the capsule and it.
Folic acid needs an enzyme that humans are poorly equipped with. Pteroylmonoglutamic acid is fully oxidized and must be reduced twice by dihydrofolate reductase to reach tetrahydrofolate before anything can be done with it. Human liver dihydrofolate reductase activity is extremely slow and varies roughly fivefold between individuals, which sets a low ceiling on how much folic acid can be converted per hour Bailey 2009. 5-MTHF bypasses that step entirely.
The enzyme after that is where the genetics live. Methylenetetrahydrofolate reductase commits 5,10-methylenetetrahydrofolate irreversibly to the methyl form. The common C677T variant produces a thermolabile enzyme with reduced activity, and homozygotes have lower plasma folate and higher homocysteine Frosst 1995. Supplying 5-MTHF puts the product of that enzyme directly into circulation and makes the variant irrelevant to plasma folate.
What the folate cycle is FOR is two things, and only one of them is homocysteine. 5-MTHF donates its methyl group to homocysteine through methionine synthase, which needs methylcobalamin as its cofactor, regenerating methionine and tetrahydrofolate. The tetrahydrofolate then re-enters the cycle to carry one-carbon units into purine and thymidylate synthesis. DNA synthesis is the older and more important job; homocysteine disposal is the one with a blood test.
And there is a trap in the cycle with a name. If vitamin B12 is deficient, methionine synthase cannot run, 5-MTHF accumulates and cannot be recycled, and the cell becomes functionally folate deficient while plasma folate looks high. That is the methyl trap, and it is why folate and B12 are a package rather than two products.
Cell, rodent, human — and where it stops
The marker end of this chain is one of the great successes of nutritional biochemistry. The outcome end is one of its most complete failures.
In cells and in enzymology. The dihydrofolate reductase bottleneck was measured directly in human liver preparations and is not a modeling result Bailey 2009. The C677T variant's effect on enzyme thermolability was characterized when the variant was first described Frosst 1995.
In humans the bioavailability question has a clean answer. [6S]-5-methyltetrahydrofolate raised plasma folate more effectively than an equivalent dose of folic acid in women, in both C677T homozygotes and wild types Prinz-Langenohl 2009. So the form argument on the label is correct as far as it goes.
In neural tube defect prevention, which is the one place folate has an outcome, the evidence belongs to folic acid. Every randomized trial and every fortification program that reduced neural tube defects used folic acid. A narrative review comparing the two forms for that indication is explicit that 5-MTHF has not been shown equivalent on the outcome, only on the marker Samaniego-Vaesken 2024. That is the reverse of the usual situation and it is worth stating loudly.
In cardiovascular prevention the surrogate collapsed completely. Meta-analysis of 8 randomized trials in 37,485 people found that lowering homocysteine with B vitamins produced no significant effect on major vascular events, cancer or cause-specific mortality Clarke 2010, and later meta-analyses in stroke and coronary populations reach the same place Kataria 2021. The homocysteine fell every time. Nothing followed it.
The obstacle to transfer is that homocysteine was a marker of risk and never a mediator of it. Elevated homocysteine associates with vascular disease in observational data, and Mendelian and randomized evidence together say the association is not causal in well-nourished populations. That is the cleanest example in this entire cohort of a number that moves without anything moving behind it.
Methylfolate (5-MTHF) — which form, and does it matter
Two salts are sold and they are not the same material. Calcium L-methylfolate and the (6S)-5-methyltetrahydrofolic acid glucosamine salt differ in crystal stability and hygroscopicity; the glucosamine salt is the more stable of the two and is what most high-end products now use. Both deliver the same anion. Neither is 'folinic acid', which is a different molecule entirely.
Stereochemistry is the form question that decides potency. Only the (6S) diastereomer is biologically active. Racemic material contains (6R)-5-MTHF, which is not used, competes for transport and is cleared slowly. A label reading '1,000 mcg 5-MTHF' without specifying (6S) or L- may be declaring twice the number of active micrograms it delivers.
The exposure arithmetic and the reason the dose looks small. 5-MTHF is absorbed by the proton-coupled folate transporter in the proximal small intestine, peaks in plasma at roughly 1 to 2 hours, and does not require the intestinal or hepatic reduction that makes folic acid's first-pass metabolism rate-limited Bailey 2009. Once inside cells it is polyglutamated by folylpolyglutamate synthetase, which traps it; whole-body turnover is therefore slow, with a functional half-life measured in weeks even though plasma clearance is fast. Excess is renally cleared.
Dietary folate equivalents are the unit and they trip everybody. Because folic acid is more efficiently absorbed than food folate, 1 mcg of folic acid counts as 1.7 mcg of dietary folate equivalents, and 5-MTHF salts have their own conversion factor. A capsule declaring 1,000 mcg of 5-MTHF and one declaring 1,700 mcg DFE can be the same capsule.
The one thing the methylated form does not fix. Unmetabolized folic acid appears in plasma when intake exceeds the reductase ceiling, and women in mandatory fortification countries taking a supplement on top of fortified food can exceed the tolerable upper intake level for folic acid without intending to Ledowsky 2022. 5-MTHF avoids generating unmetabolized folic acid. It does not undo what a fortified diet is already contributing, and the upper limit is set on the synthetic acid rather than on total folate.
What would have to be true, and how you would know it was not
1. Serum and red cell folate will rise, and the red cell number is the one worth waiting for. Predict folate, serum rises within 2 weeks on 1 mg daily and folate, RBC rises over 12 to 16 weeks, because the red cell measure reflects the folate incorporated during erythropoiesis Prinz-Langenohl 2009. Retest RBC folate at 16 weeks, not at 4.
2. Homocysteine will fall and that is the least surprising result in nutrition. Predict homocysteine down by roughly a quarter within 8 weeks on 1 mg, more in a C677T homozygote and more again if B12 and B6 are supplied alongside Kataria 2021. Retest at 8 to 12 weeks.
3. The prediction that cuts against the product, and it is the reason this page exists. Predict that the homocysteine fall is followed by no change in cardiovascular events, because 37,485 randomized people returned exactly that Clarke 2010. A modern trial in a homocysteine-selected population showing event reduction would falsify this page. So would a Mendelian randomization study establishing causality that the existing ones have not.
4. Predict that a normal folate does not exclude a B12 problem, and check the pair. Order vitamin B12 and methylmalonic acid (MMA) alongside folate before starting, and predict that supplementing folate alone in a B12-deficient person normalizes the blood count while the neurological picture continues. That is the oldest known harm in this field and it is entirely preventable by one extra test.
5. Predict genotype changes the size of the effect and not the direction. If MTHFR C677T has been run, predict a homozygote shows a larger homocysteine fall and a larger plasma folate rise on 5-MTHF than on folic acid, and predict a wild type shows a smaller difference between the two forms Prinz-Langenohl 2009 Frosst 1995. A genotype-stratified trial finding no difference would falsify the central marketing claim for this product.
What nobody has tested yet
The neural tube defect trial for 5-MTHF has never been attempted. Folic acid has the outcome evidence; 5-MTHF has the marker evidence and is increasingly what prenatal products contain Samaniego-Vaesken 2024. Substituting a form on the strength of a biomarker, in the one indication where folate has a proven outcome, is a decision the field made without a trial.
Nobody knows whether unmetabolized folic acid is harmful. It is measurable in plasma in fortified populations, it has been associated in observational work with reduced natural killer cell cytotoxicity and with masked B12 deficiency, and no interventional study has demonstrated a clinical consequence Ledowsky 2022. That uncertainty is the main argument for the methylated form and it is an argument from absence.
The dose ceiling for 5-MTHF has never been established. The tolerable upper intake level is written for folic acid because that is what the masking data are about. There is no corresponding number for 5-MTHF, which means products at 5 and 15 mg are sold into a regulatory vacuum rather than under a demonstrated ceiling.
And the psychiatric adjunct question is unresolved. L-methylfolate at 15 mg is used as an adjunct in depression on the theory that folate limits monoamine synthesis through tetrahydrobiopterin regeneration. The trials are small, the replication is partial, and the mechanism has never been demonstrated in a human brain.
Methylfolate (5-MTHF) — its own safety story, not its category's
The specific hazard of folate is that it fixes the wrong half of a B12 deficiency. Folate supplementation corrects the megaloblastic anemia of B12 deficiency because the DNA synthesis block is folate-responsive, while the neurological damage — subacute combined degeneration — continues, because that arm depends on methylmalonyl-CoA mutase and needs adenosylcobalamin. The blood count that would have triggered investigation goes back to normal. This is the reason folate and B12 are tested together.
The upper limit is about the synthetic acid, not about folate. The tolerable upper intake level for adults is 1,000 mcg per day of folic acid from supplements and fortified foods, and it exists specifically because of the masking problem above. Women taking a supplement in a mandatory fortification country routinely exceed it Ledowsky 2022.
The interactions worth naming are with drugs that target the same enzyme. Methotrexate is a dihydrofolate reductase inhibitor and folate supplementation is deliberately used to reduce its toxicity, which means the timing and form are a clinical decision rather than a supplement decision. Anticonvulsants including phenytoin, carbamazepine and valproate lower folate; folate in turn can lower phenytoin concentrations. Sulfasalazine and trimethoprim both interfere with folate handling.
A note on the methylation reaction itself. Some people report agitation, irritability or insomnia on starting a methylated folate, particularly at milligram doses. There is no controlled evidence characterizing this, and the honest description is that it is commonly reported and unstudied rather than either established or dismissed.
Who needs a clinician rather than a page. Anyone with a history of colorectal adenoma, since high-dose folate has an unresolved association with adenoma recurrence; anyone on methotrexate; anyone pregnant, because the dose and form decisions there have an outcome attached Samaniego-Vaesken 2024. Nothing here is medical advice or diagnosis, and these statements have not been evaluated by the Food and Drug Administration.
Sources read for this page
- Bailey SW, et al. The extremely slow and variable activity of dihydrofolate reductase in human liver and its implications for high folic acid intake. Proceedings of the National Academy of Sciences 2009 · PMID 19706381
- Prinz-Langenohl R, et al. [6S]-5-methyltetrahydrofolate increases plasma folate more effectively than folic acid in women with the homozygous or wild-type 677C-->T polymorphism of methylenetetrahydrofolate reductase. British Journal of Pharmacology, 2009 · PMID 19917061
- Frosst P, et al. A candidate genetic risk factor for vascular disease: a common mutation in methylenetetrahydrofolate reductase. Nature Genetics, 1995 · PMID 7647779
- Samaniego-Vaesken ML, et al. Supplementation with Folic Acid or 5-Methyltetrahydrofolate and Prevention of Neural Tube Defects: An Evidence-Based Narrative Review. Nutrients 2024 · PMID 39339754
- Clarke R, et al. Effects of lowering homocysteine levels with B vitamins on cardiovascular disease, cancer, and cause-specific mortality: Meta-analysis of 8 randomized trials involving 37 485 individuals. Archives of Internal Medicine, 2010 · PMID 20937919
- Ledowsky C. Women Taking a Folic Acid Supplement in Countries with Mandatory Food Fortification Programs May Be Exceeding the Upper Tolerable Limit of Folic Acid: A Systematic Review. Nutrients 2022 · PMID 35807899
- Kataria N. Effect of Vitamin B6, B9, and B12 Supplementation on Homocysteine Level and Cardiovascular Outcomes in Stroke Patients: A Meta-Analysis of Randomized Controlled Trials. Cureus 2021 · PMID 34123655
How you would know if it worked
These are the markers that recommend this product on their own pages, so they are the ones that should move if it is doing what it is sold for.
- MTHFR, DNA Analysis — Methylfolate (5-MTHF) 400–1,000 mcg instead of folic acid, plus methylcobalamin B12 and P5P (B6) Retest: Never — fixed for life.
- Folate, Serum — Methylfolate (5-MTHF) 400–1,000 mcg — preferred over folic acid, especially with MTHFR variants Retest: 8–12 weeks after supplementation.
- Folate, RBC — Methylfolate (5-MTHF) 400–1,000 mcg, always alongside B12 Retest: 12 weeks after supplementation.
- Homocysteine — Methylfolate 400–1000 mcg + methylcobalamin (B12) 1000 mcg + P5P (B6) 25–50 mg is the standard stack Retest: 8–12 weeks after starting B vitamins.
The cheapest panel carrying Folate, Serum and at least one other of these is On Metformin — the B12 Nobody Checks, at $170 — the panel is named for a different question, and the marker is the same marker. That is the whole cost of finding out.
Draw before you start, not after. A result with nothing to compare it to answers nothing.
Methylfolate (5-MTHF) — safety & side effects
- Well tolerated. Some people report irritability, anxiety or insomnia on methylfolate specifically, which usually means the dose is too high.
- Folate above 1,000 mcg/day can mask B12 deficiency — correcting the anemia while the neurological damage continues. Always pair with B12.
- Reduces the effectiveness of methotrexate and some antiepileptics (phenytoin, phenobarbital). If you are on methotrexate for cancer rather than for inflammation, this matters — ask before adding it.
Not medical advice. If you take prescription medication or have a diagnosed condition, check this against it with a pharmacist or doctor — pharmacists are underused and free.
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The full Supplement Vault — 371 products across 14 categories with clinical, correlative & theoretical evidence, plus my Thorne partner links — lives inside Skool alongside 278 peptides.
Join Skool — $10/mo →Bloodwork to run alongside Methylfolate (5-MTHF)
Baseline first, then again at 8–12 weeks.
| Marker | What it’s watching for |
|---|---|
| Folate, Serum | The level you're correcting |
| Vitamin B12 | Folate can mask a B12 deficiency while nerve damage continues |
| Methylmalonic Acid (MMA) | The test that stops that from happening |
| MTHFR, DNA Analysis | Explains why some people need the methylated form |
| Homocysteine | The functional read on whether it's working |
The Full Micronutrient Screen panel covers these in one order — 11 markers, $363.60 with the discount applied.
Check results you already have → · All 103 markers A–Z
Methylfolate (5-MTHF) — frequently asked questions
What is Methylfolate (5-MTHF)?
The active, bioavailable form of folate (vitamin B9) that bypasses the MTHFR conversion step, so it works even in the ~40% of people who methylate folic acid poorly.
What is the suggested dose of Methylfolate (5-MTHF)?
1 mg daily (higher only under guidance). This is a general reference for education only — statements have not been evaluated by the FDA and this is not medical advice.
What are the researched benefits of Methylfolate (5-MTHF)?
Lowers homocysteine and raises red-cell folate more reliably than folic acid in MTHFR carriers (RCT-supported).
Who is Methylfolate (5-MTHF) for?
MTHFR variants, preconception/pregnancy, methylation and mood support.
Where can I buy Methylfolate (5-MTHF)?
Coach Cam sources Methylfolate (5-MTHF) from Thorne, with 10% off auto-applied at checkout — use the buy link on this page.
Methylfolate (5-MTHF) inside a finished plan
One arm of 3 Protocol Blueprints, free to read in full.
What Methylfolate (5-MTHF) is used for
Methylfolate (5-MTHF) appears under 5 goals in the goal router.
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Where this goes next
Methylfolate (5-MTHF) is the boring-causes arm of this plan. The page above is the free breakdown of one compound; the plan it belongs to — the dosing, the order to correct things in, the week-by-week schedule and what to retest — is a lesson inside Skool.