Bisson ND, 5-MTHF5 MTHF, provided as Quatrefolic, is the most biologically active form of the water soluble B vitamin, folic acid. It is the preferred form of folate supplementation due to an array of conditions that can limit the conversion or absorption of folic acid. Data indicate that supplementing with 5 MTHF increases plasma folate more effectively than folic acid.* LEARN MORE *Follow recommended dosing or use as directed by your healthcare practitioner.