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L-methylfolate

Supplement folate form women's healthgeneral nutrition
Aka: 5-MTHF, methylfolate, L-5-methyltetrahydrofolate
Brands seen in Singapore: California Gold Nutrition, Jarrow Formulas, NOW Foods, Doctor's Best, Life Extension
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
DNA and amino-acid work · folate's main form in plasma
When to take
No timing rule
Take with
With adequate B12 · high folate can mask a B12 deficiency
Pros & cons
Pros
  • Bioavailability equals or beats folic acid
  • Some with the mthfr 677c>t variant may benefit
  • 15,000 mcg/day as an SSRI add-on — low-quality evidence
Cons
  • Cdc advises folic acid, not 5-mthf, before pregnancy
  • No formal mcg to mcg dfe conversion factor exists
  • High folate can mask a B12 deficiency
Sources
  1. NIH ODS — Folate (Health Professional), updated November 30, 2022 — Introduction (read via archive.org capture, see verify_notes) · read 2026-08-27
    what it says
    “Some dietary supplements also contain folate in the monoglutamyl form, 5-MTHF (also known as L-5-MTHF, 5-methyl-folate, L-methylfolate, and methylfolate) … The main form of folate in plasma is 5-MTHF”
  2. NIH ODS — Folate (Health Professional) — Introduction, function · read 2026-08-27
    what it says
    “Folate functions as a coenzyme … in single-carbon transfers in the synthesis of nucleic acids (DNA and RNA) and metabolism of amino acids”
  3. NIH ODS — Folate (Health Professional) — Sources of Folate, dietary supplements · read 2026-08-27
    what it says
    “The bioavailability of 5-MTHF in supplements is the same as or greater than that of folic acid … However, conversion factors between mcg and mcg DFE for 5-MTHF have not been formally established”
  4. NIH ODS — Folate (Health Professional) — Groups at Risk, MTHFR 677C>T polymorphism · read 2026-08-27
    what it says
    “some of these people might benefit from supplementation with 5-MTHF. However, the Centers for Disease Control and Prevention (CDC) recommends 400 mcg/day of folic acid, not 5-MTHF, for people who could become pregnant”
  5. NIH ODS — Folate (Health Professional) — Table 1 RDAs and the DV note · read 2026-08-27
    what it says
    “19+ years 400 mcg DFE 400 mcg DFE 600 mcg DFE 500 mcg DFE … The DV for folate is 400 mcg DFE for adults and children age 4 years and older”
  6. NIH ODS — Folate (Health Professional) — Health Risks from Excessive Folate; Table 3 ULs · read 2026-08-27
    what it says
    “the FNB established a UL for the synthetic forms of folate available in dietary supplements and fortified foods … 19+ years 1,000 mcg … The ULs do not apply to individuals taking high doses of supplemental folate under medical supervision”
  7. NIH ODS — Folate (Health Professional) — Health Risks, masking of vitamin B12 deficiency · read 2026-08-27
    what it says
    “Large amounts of folate can correct the megaloblastic anemia, but not the neurological damage, that can result from vitamin B12 deficiency … high intakes of folate supplements might mask vitamin B12 deficiency”
  8. NIH ODS — Folate (Health Professional) — Folate and Health, depression · read 2026-08-27
    what it says
    “a systematic review and meta-analysis of three trials of 5-MTHF … concluded that 15,000 mcg/day 5-MTHF might be an effective adjunct to SSRI therapy in patients with major depressive disorder, although … this conclusion was based on low-quality evidence”
  9. NIH ODS — Folate (Health Professional) — Interactions with Medications · read 2026-08-27
    what it says
    “Methotrexate … is a folate antagonist … the supplements could interfere with methotrexate's anticancer effects … Antiepileptic medications … can reduce serum folate levels … Sulfasalazine … inhibits the intestinal absorption of folate”
  10. HSA Singapore — Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines, GL-CHPB-1-012 Rev. No. 001 (October 2025), Annex A row 47 · read 2026-08-27
    what it says
    “47. Folic acid Restricted use in HS and TM Maximum Daily Dose When for oral use by general adult population, the maximum recommended daily dose should not provide more than 0.9mg”
  11. HSA Singapore — Health Supplements Guidelines GL-CHPB-3-001 Rev. No. 020 (January 2026), clause 4.8 and Table 4 Vitamins Limits · read 2026-08-27
    what it says
    “4.8 HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5 … Table 4: Vitamins Limits … Folic acid 0.9mg”
  12. iHerb Singapore — Vitamin B9 (Folate - Folic Acid) category page, default listing order · read 2026-08-27
    what it says
    “Vitamin B9 … 130 results … California Gold Nutrition, Folinic Acid … Jarrow Formulas, Vegan Methyl Folate … NOW Foods, Folic Acid … Doctor's Best, Fully Active Folate … Life Extension, BioActive Folate & Vitamin B12”
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Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.