Solgar Folate 666 mcg DFE (Metafolin 400 mcg) Review
#4 of 9 · Best for MTHFR✓ Label verified · Supplement Facts read Sep 7, 2026Real retailer photo, cut out. Label unedited.
Consider it. The best methylfolate — for the people who actually need it. Bioidentical L-5-MTHF at the correct dose from a reputable brand.
$20 approx~$0.20 / tablet
Why It Scores 7.5 — And The Label Line Behind Each Number
Form & Evidence Base
30% of scoreL-methylfolate raises folate status effectively but has no randomized NTD-prevention trials — the evidence gap versus folic acid is real and drives this ranking. Metafolin is bioidentical L-5-MTHF, absorbed directly with no conversion step.
- Form
- L-methylfolate tablet (Metafolin)
Dose vs Clinical Target
25% of score400 mcg is a well-judged folate dose, and it sits within the prenatal target range — unlike the 1 mg options. The label does not print a DFE-converted figure for this form, so we score the dose on the plain 400 mcg amount.
- Dose
- 400 mcg L-5-MTHF
Third-Party Testing & Purity
20% of scoreNon-GMO, vegan, kosher and gluten-free, but no independent USP audit.
- Testing / Certification
- Non-GMO, Vegan, Gluten Free, Kosher
Tolerability & Safety
15% of scoreA sensible, clean option — genuinely useful for those with reduced MTHFR enzyme activity, and it raises folate status effectively even in MTHFR carriers.
Value
10% of scoreAround $20 for 100 tablets — reasonable within the methylfolate category, but several times the cost-per-dose of folic acid.
- Count
- 100 tablets
- Cost per dose
- ~$0.20 per tablet
Label verified. Every figure read from the Supplement Facts photo, Sep 7, 2026.
Marketing Claims Vs. Reality
Methylfolate needs no conversion so it's better for MTHFR carriers
L-5-MTHF bypasses the MTHFR-dependent conversion step and raises folate as effectively as folic acid even in 677TT women (Prinz-Langenohl 2009, PMID 19917061), but this benefit is meaningful mainly for those with a confirmed variant.
Methylfolate prevents neural-tube defects as well as folic acid
No randomized trial has tested methylfolate for NTD prevention. Reviews note folic acid remains the form with proven periconceptional benefit (Obeid 2013, PMID 23482308).
What Our Test Actually Found
Correction: the label states 400 mcg, no DFE figure
An earlier version of this review listed the dose as "666 mcg DFE" alongside the 400 mcg amount. The Supplement Facts panel prints only "Folate 400 mcg (as L-methylfolate as Metafolin)" — no DFE-converted number appears anywhere on the label. We re-read the label on Sep 7, 2026 and corrected the product name, lead, dose spec, and every buy/pro bullet that repeated the unlabeled 666 mcg DFE figure.
Right form for a specific person, not the general population
For a woman with a documented MTHFR 677TT genotype or established methylation concerns, Metafolin is a rational choice. For everyone else it solves a problem they likely do not have.
Bioequivalence is not the same as outcome equivalence
Studies show methylfolate matches folic acid at raising blood folate — but 'raises folate levels' and 'prevents birth defects' are different endpoints. Only folic acid has the second.
Full analysis: all pros & cons (7), buy if / skip if
- Bioidentical L-5-MTHF, no conversion step required
- Correct 400 mcg prenatal dose
- Trusted brand with clean vegan/non-GMO certifications
- Best-judged dose among the methylfolate options
- Raises folate status effectively even in MTHFR carriers
- No NTD-prevention trial evidence for the methylfolate form
- Roughly five times the cost per dose of folic acid
- Bioidentical L-5-MTHF, no conversion step required
- Correct 400 mcg prenatal dose
- Trusted brand with clean vegan/non-GMO certifications
- No NTD-prevention trial evidence for the methylfolate form
- Roughly five times the cost per dose of folic acid
Bioidentical L-5-MTHF at the correct dose from a reputable brand. Genuinely useful for confirmed MTHFR variants, but it costs several times more than folic acid and lacks NTD-prevention trial data, so it is not the default.
This is our top methylfolate pick, and it is honest about what that means. Solgar uses Metafolin, a bioidentical L-5-MTHF that needs no enzymatic conversion, at 400 mcg — the right dose. For someone with a documented MTHFR variant or a preference to bypass conversion, it is a sensible, clean option from a trusted brand. But note the ranking: it sits below every folic acid pick because methylfolate has no NTD-prevention trial evidence. It raises blood folate as well as folic acid does; it has simply never been tested against the outcome that matters for pregnancy. Pay the premium only if you have a specific reason to.
Buy it for a reason, not by default
This is the methylfolate to choose if you genuinely need methylfolate — a confirmed MTHFR variant, a clinician's direction, or documented intolerance to folic acid. It is well-formulated and correctly dosed. But it ranks below the folic acid picks because the NTD evidence lives with folic acid, and paying five times more for an unproven-for-that-outcome form is not the smart default.
If This Doesn’t Fit — Try These
01Nature Made 400 mcg
This is the default folate for nearly every woman: the proven form, the proven dose, and the one product here carrying USP verification.
05Pure Encapsulations 400
If you're set on methylfolate and prioritize purity, this is the cleanest option here — hypoallergenic, tested, and filler-free.
Quick Answers
Do I need methylfolate if I have an MTHFR variant?
Not necessarily. Most MTHFR carriers still convert folic acid adequately and are protected by standard doses. Methylfolate is a reasonable option if you have a confirmed variant or clinician guidance, but it is not required for most people.
Why is a more 'advanced' form ranked below plain folic acid?
Because our method weights proven outcomes. Methylfolate raises folate levels well but has never been tested for preventing neural-tube defects, whereas folic acid has strong trial evidence.
Sources & Further Reading
2 peer-reviewed sources, each linked to PubMed
- [1] Prinz-Langenohl R, Brämswig S, Tobolski O, 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. Br J Pharmacol. 2009;158(8):2014-21. PMID 19917061 — [6S]-5-methyltetrahydrofolate increases plasma folate more effectively than folic acid in women with the 677C→T MTHFR polymorphism. 5-MTHF raised plasma folate at least as effectively as folic acid, including in 677TT women.
- [2] Obeid R, Holzgreve W, Pietrzik K. Is 5-methyltetrahydrofolate an alternative to folic acid for the prevention of neural tube defects? J Perinat Med. 2013;41(5):469-83. PMID 23482308 — Is 5-methyltetrahydrofolate an alternative to folic acid for the prevention of neural tube defects?. Concludes 5-MTHF is a plausible but unproven alternative; folic acid retains the trial evidence for NTD prevention.
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