At the center of a hemoglobin molecule is iron and when combined with oxygen, it gives arterial blood its bright red  color. Hemoglobin transports oxygen in the blood from the lungs to the tissues which need oxygen to maintain basic  life functions. Iron is also necessary for the formation of myoglobin, found only in muscle tissue, which supplies oxygen to the muscle cells.

Significant amounts of iron can be lost during menstruation and needs are higher for pregnant women. Protein and  vitamin C aid in the absorption of iron by chelating or attaching onto the iron ion and carrying it across the intestinal  walls.
Excess iron can accumulate in the body to toxic levels. Take iron supplements only on the advice of a physician.