Quest Once a Day Iron Plus provides iron, vitamin C, vitamins B2, niacin, B6, B12, pantothenic acid and folic acid which contribute to the reduction of tiredness and fatigue. Iron plays a role in the transport of vital oxygen around the body and in the formation of red blood cells. Quest Synergistic Iron provides a gentle form of iron chelated with amino acids and additional nutrients to aid in its absorption and utilisation in the body.