B12 BOOSTB 12 Boost provides 5 mg (5000 mcg) of vitamin B12 in each very small, pleasant tasting tablet. Methylcobalamin, the form of B12 active in the body, appears to be better absorbed and stored in tissues in comparison to cyanocobalamin. Methylcobalamin has multiple supportive roles in the body, including red blood cell formation, nervous system health, homocysteine and folate metabolism, melatonin synthesis, and more.