Iron and ferritin — what’s the difference?

Women with symptoms of anemia or an abnormal CBC (complete blood count) are often sent by their practitioners to get a ferritin and/or iron test. If anemia is suspected and the patient hasn’t had one recently, a CBC is also ordered.

Another important cause of a low iron or anemic state could be an internal bleed somewhere in the body, so the healthcare practitioner will likely consider this option as well.

Many women with are confused by what the lab results of each of these mean. There are three basic medical tests that practitioners use to assess how iron is working in your body:

• Serum iron: measures amount of iron in your blood
• Total iron-binding capacity (TIBC): measures the amount of transferrin, the protein responsible for transferring iron from your gut to your cells and bone marrow
• Serum ferritin: measures the amount of iron you have stored in your body

Iron is an essential part of hemoglobin, the protein in our red blood cells that carries oxygen from our lungs to the rest of the body. Without enough iron, we can end up anemic, with symptoms of fatigue, weakness, shortness of breath and dizziness, to name a few, as well as decreased immune function. Anemia can also develop when the body cannot use iron properly, which happens in people with chronic diseases such as cancer and autoimmune disorders, and in those with ongoing infections.

A simple iron or ferritin test may not provide the complete picture. It’s important to determine the root of the issue before deciding on a treatment path. This oftentimes means doing all three medical tests mentioned above, and sometimes others as well. In situations where you have adequate iron but you are not using it properly, your ferritin will likely be high while your transferrin and serum iron will be low. On the other hand, if you don’t have enough iron in the body, serum iron and ferritin will be low, while transferrin will be high. Understanding these relationships will give us a better idea about the cause of anemia.

Published: October 10, 2013 - Last Updated: April 7, 2021