Metafolin® ((6S)-5-methyltetrahydrofolic acid, calcium salt or L-methylfolate) is the pure stable crystalline form of the naturally-occurring predominant form of folate.

Folates are water-soluble B-vitamins, which play a key role in central metabolic pathways. Folates are, for example, needed for cell division or cell repair. Metafolin® is L-methylfolate, the body's preferred form of folate. Metafolin® is directly usable by the human organism, directly involved in lowering homocysteine blood levels, and the only form of folate able to cross the blood-brain barrier.