Iron

The serum iron test measures the amount of iron in the liquid portion of blood. Iron is an essential trace element that is absorbed from food and transported throughout the body by transferrin, a protein produced by the liver. Iron is necessary for the production of healthy red blood cells (RBCs). It is an important part of hemoglobin, the protein in RBCs that enables them to carry oxygen throughout your body. Iron is also used in the production of some proteins, including myoglobin and some enzymes.

Normally, about 70% of the iron absorbed is incorporated into the hemoglobin inside RBCs. Most of the rest is stored in the tissues as ferritin or hemosiderin. If not enough iron is taken in from the diet, then levels in the blood may drop, which then can deplete iron stored in the body. Over time, low blood levels and decreased iron stores can lead to iron deficiency anemia. On the other hand, absorption of too much iron can lead to progressive accumulation and damage to organs such as the liver, heart, and pancreas.

The serum iron test measures the amount of iron that is in transit in the body – the iron that is bound to transferrin. The amount of iron present in the blood will vary throughout the day and from day to day. For this reason, serum iron is almost always measured with other iron tests, such as the total iron-binding capacity (TIBC), from which the transferrin saturation can be calculated. Transferrin saturation reflects the amount of iron being transported in the blood and its capacity to carry more. The use of several iron tests provides a more reliable measure of iron deficiency and iron overload than measuring serum iron by itself.

A blood sample is drawn by needle from a vein in your arm.

Morning samples are preferred. You may be instructed to fast for twelve hours before sample collection. In this case, only water is permitted.