5-MTHF ES provides 17,000 mcg of 5-MTHF (5-methyltetrahydrofolate) per serving. 5-MTHF is the most biologically active form of the water-soluble B vitamin, folate;  and it may be the preferred form for those with variations in digestion, absorption, or folate metabolism. Data suggest that in comparison to synthetic folic acid, 5-MTHF increases plasma folate more effectively. In this formula, 5-MTHF is provided as Quatrefolic^®—the glucosamine salt of 5-MTHF. Quatrefolic has demonstrated greater stability, solubility, and bioavailability when compared to calcium salt forms of 5-MTHF.*