A person's blood contains roughly 70% of the total iron in the body. Iron is carried in the hemoglobin of the red blood cells. Iron from food is absorbed into the plasma through the small intestine. Once in the bloodstream, the iron binds to a blood protein that transports it to the bone marrow. There it is incorporated into the hemoglobin. The serum iron test measures the amount of iron in the plasma that is on its way to the bone marrow.

Who is a candidate for the test?

A serum iron test is done on someone who is suspected of having too little iron in the blood. It is also performed on a person who may have an overload of iron in the blood.

How is the test performed?

To measure the serum iron, a blood sample is needed. This is usually taken from a vein on the forearm or hand. First, the skin over the vein is cleaned. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them.

A fine needle is gently inserted into the chosen vein, and the tourniquet is removed. Blood flows from the vein through the needle. It is collected in a syringe or vial for testing in the lab. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding .