Serum iron is a test that measures how much iron is in your blood.

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with a substance that prevents bacteria (antiseptic). An elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a tube attached to the needle (syringe). The band is removed to let blood flow normally. Once the blood has been collected, the needle is removed, and the site is covered to stop any bleeding.

In an infant or young child:

The area is cleaned with antiseptic and then a sharp needle or a small knife (lancet) is inserted. The blood may be collected in a small glass tube (pipette), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be placed on the puncture site if bleeding continues.

These is no special preparation for this test.

When the needle is inserted to draw blood, some people feel moderate pain. Others will feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Your doctor may order this test if you have signs of low iron (iron deficiency).

• Iron: 60-170 mcg/dl
• TIBC: 240-450 mcg/dl
• Transferrin saturation: 20-50%

Note: mcg/dl = micrograms per deciliter

Higher-than-normal levels may mean:

• Hemochromatosis
• Hemolysis
• Hemolytic anemias
• Hemosiderosis
• Liver tissue death (hepatic necrosis)
• Hepatitis
• Vitamin B-12 deficiency, vitamin B-6 deficiency
• Iron poisoning
• Many blood transfusions

Lower-than-normal levels may mean:

• Chronic gastrointestinal blood loss
• Chronic heavy menstrual bleeding
• Poor absorption of iron
• Not enough dietary iron
• Pregnancy

Other conditions under which the test may be performed:

• Anemia of chronic disease

• Excess bleeding
• Fainting or feeling light-headed
• Blood under the skin (hematoma)
• Infection
• Many punctures to find veins

Drugs that can increase iron include chloramphenicol, estrogens, oral birth control, and methyldopa.

Drugs that can lower iron include cholestyramine, chloramphenicol, colchicine, deferoxamine, methicillin, allopurinol, and testosterone.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Getting a blood sample from some people may be more difficult than from others.

Heeney MM, Andrews NC. Iron homeostasis and inherited iron overload disorders: an overview. Hematol Oncol Clin North Am. December 2004;18:1379-1403.

Pieracci FM, Barie PS. Diagnosis and management of iron-related anemias in critical illness. Crit Care Med. July 2006;34:1898-1905.