Methylfolate (5-MTHF) Dosage Calculator

What is Methylfolate (5-MTHF)?

5-Methyltetrahydrofolate (5-MTHF, methylfolate) is the predominant circulating form of folate and the only form that crosses the blood-brain barrier. It donates methyl groups to homocysteine (converting it to methionine) and to biopterin (regenerating BH4, the essential cofactor for serotonin, dopamine, and nitric oxide synthesis). Folate deficiency causes megaloblastic anaemia, elevated homocysteine (cardiovascular risk), and — critically in early pregnancy — neural tube defects (spina bifida, anencephaly). Supplementation reduces NTD risk by 70% when begun at least 1 month before conception. **MTHFR polymorphisms:** The MTHFR C677T variant (homozygous in ~10% of populations, heterozygous in ~40%) reduces the enzyme that converts dietary folate and synthetic folic acid to 5-MTHF by 70–90%. Individuals with this variant cannot effectively utilise folic acid from supplements or fortified foods — they require pre-formed methylfolate (5-MTHF) directly. Given the prevalence of this variant, methylfolate is the clinically prudent choice over folic acid for all supplementation. Consider MTHFR genetic testing if you have a history of recurrent pregnancy loss, depression resistant to antidepressants, or elevated homocysteine. Always consult your obstetrician or GP before adjusting folate supplementation during preconception or pregnancy.

How to Take Methylfolate (5-MTHF)

**RDA:** 400 mcg DFE/day (adults); 600 mcg DFE during pregnancy; 500 mcg during breastfeeding. **UL:** 1,000 mcg/day for synthetic folic acid (the UL does not apply to naturally occurring or supplemental 5-MTHF, which lacks the masking-B12-deficiency concern). **Supplemental 5-MTHF:** 400–800 mcg/day for general health and preconception; 800–1,000 mcg/day during pregnancy; 1,000–5,000 mcg/day under physician supervision for MTHFR homozygotes or documented hyperhomocysteinaemia.

Timing Recommendations

Take with or without food. Consistent daily timing matters more than meal co-administration. Morning dosing with B12 (the methyl-cycle cofactor) is rational. Avoid very high-dose methylfolate in the evening — it may cause vivid dreams or sleep disruption in a minority of individuals due to neurotransmitter upregulation.

Potential Side Effects & Safety

5-MTHF is very well tolerated. Some individuals with anxiety, bipolar disorder, or undermethylation phenotypes experience "overmethylation" symptoms (irritability, anxiety, insomnia) when starting high doses — start at 400 mcg and titrate upward slowly. Unlike synthetic folic acid, there is no established UL for 5-MTHF and it does not mask vitamin B12 deficiency.

Best Stacks with Methylfolate (5-MTHF)

The methylation triad: methylfolate (5-MTHF, 400–800 mcg) + methylcobalamin B12 (1,000 mcg) + P5P B6 (50 mg) — optimises the homocysteine-to-methionine remethylation cycle. For pregnancy: methylfolate + choline (450 mg) + DHA (200 mg) covers the three primary fetal neurodevelopmental nutrients.

Scientific References

All dosage recommendations are grounded in peer-reviewed research.

1. 1
   Prevention of neural tube defects: results of the Medical Research Council Vitamin Study

   The Lancet · 1991

2. 2
   MTHFR C677T polymorphism and folic acid supplementation

   Nutrients · 2020