Iron Saturation (%)

Iron saturation, also called transferrin saturation or TSAT, shows what percentage of your transferrin is currently carrying iron. It gives you a clearer view of how much iron is actually available for your body to use than serum iron measured on its own.

Ranges vary between labs, so compare to the range on your own lab report.

What iron saturation measures

Transferrin is the main protein that carries iron through your blood. Iron saturation is calculated by dividing your serum iron by your total iron-binding capacity and multiplying by 100, so it reports the percent of transferrin binding sites that are occupied by iron. A result of 30 percent means roughly a third of your available transport capacity is filled.

What high or low levels mean

A low iron saturation usually means your body does not have enough circulating iron, which often reflects iron deficiency from low dietary intake, blood loss, or poor absorption. It can also fall during chronic inflammation, when iron is present but locked away and harder to use. A high saturation points toward too much iron. Values that stay above roughly 45 percent in men or 50 percent in women raise concern for iron overload conditions such as hereditary hemochromatosis, especially when confirmed on a repeat fasting sample. Because saturation reacts to recent meals, supplements, and inflammation, you should read it alongside ferritin, which reflects your stored iron. If your result sits well outside the range, ask your clinician whether repeat or genetic testing makes sense.

Iron saturation FAQ

What does a high iron saturation mean?

A high iron saturation means a large share of your transferrin is carrying iron. Persistent elevations can signal iron overload or hemochromatosis, so your clinician may repeat the test while fasting and check ferritin before ordering further evaluation.

Can iron saturation be low when iron looks normal?

Yes. During inflammation or infection your serum iron can drop while transferrin shifts, lowering saturation even when total body iron looks adequate. This is why results are interpreted together with ferritin and your overall clinical picture.

Should you fast before an iron saturation test?

Many labs prefer a morning fasting sample because iron and saturation rise after meals and iron supplements. Following your lab's preparation instructions helps you avoid a falsely high reading that could prompt unnecessary follow-up testing.

Read alongside ferritin, serum iron, and total iron-binding capacity to see your full iron status.

Sources

• MedlinePlus, Transferrin Test. U.S. National Library of Medicine.

• Adams PC, Barton JC. How I treat hemochromatosis. Blood.