Both folic acid and vitamin B12 are essential for health. But when taken together, these B vitamins may interact with each other. You shouldn't take more than 1,000 micrograms (mcg.) of supplemental folic acid per day. More than this can cause symptoms of vitamin B12 deficiency.
A synthetic form of folic acid is used in dietary supplements and fortified foods. Folic acid acts by helping the body produce and maintain new cells. In particular, red blood cell formation is dependent upon adequate levels of this vitamin. Folic aciddeficiency is a known cause of anemia in both adults and children.
For preventing an eye disease that leads to vision loss in older adults (age-related macular degeneration or AMD): 2.5 mg of folic acid, 1 mg of vitamin B12(cyanocobalamin), and 50 mg of vitamin B6 (pyridoxine) per day have been used. For preventing stroke. 500 mcg to 40 mg of folic acid per day have been used