Iron is an essential nutrient. It is needed in small quantities to help form normal red blood cells (RBCs). Iron is a critical part of haemoglobin, the protein in red blood cells that binds oxygen in the lungs and releases it as blood travels to other parts of the body. Low iron levels can lead to anaemia and the production of RBCs that are small (microcytic) and pale (hypochromic). Large quantities of iron can be toxic to the body, and absorption of too much iron over time can lead to the accumulation of iron compounds in organs and tissues. This can damage organs such as the liver, joints, heart, and pancreas.

Iron tests evaluate the amount of iron in the body by measuring several substances in the blood. These tests [namely transferrin or TIBC, ferritin] are often requested at the same time and the results considered together to help diagnose and/or monitor iron deficiency or iron overload.

Iron deficiency may be seen with insufficient intake, inadequate absorption, or increased requirements, such as may be seen during pregnancy or with acute or chronic blood loss.