5-MTHF is an active, tissue-ready form of folate. It’s an essential B vitamin that supports methylation. Many individuals don’t get sufficient 5-MTHF because they have intestinal or liver dysfunction or because of their genetic makeup. Many individuals don’t get sufficient 5-MTHF (L-5-Methyltetrahydrofolate), the active form of folic acid, because they have intestinal or liver dysfunction or because their genetic makeup makes it difficult to convert folic acid into active 5-MTHF