Doctor's Best Fully Active B Complex contains all eight important B Vitamins, a full spectrum designed for optimal absorption and utilization to support overall health and well-being. Water-soluble B vitamins play important roles in cell metabolism, supporting DNA, organs, genes, cells, tissues, skin health, immune system, enzyme functions, and energy production. Quatrefolic is the glucosamine salt of (6S)-5-methyl- tetrahydrofolate, the most bioavailable form of folate, that provides greater stability and water solubility.