Vitamin B is a class of water-soluble vitamins that play important roles in cell metabolism and synthesis of red blood cells. Though these vitamins share similar names B1, B2, B3, and so on, they are chemically distinct compounds that often coexist in the same foods. In general, dietary supplements containing all eight are referred to as a vitamin B complex. Individual B vitamin supplements are referred to by the specific number or name of each vitamin, such as B1 for thiamine, B2 for riboflavin, and B3 for niacin. Some are more commonly recognized by name than by number: niacin, pantothenic acid, biotin, and folate.