Transferrin is the protein that carries iron through the blood from the stores to the bone marrow, where red blood cells are made. It shows whether there is enough "transport" for iron.
The logic is the reverse of ferritin: when iron is scarce, the body increases transferrin production to catch every atom. So transferrin is looked at together with ferritin, TIBC and transferrin saturation.
Reference ranges
The reference depends on the lab; a typical adult range:
| Adults | 2.0 – 3.6 g/L |
| Iron deficiency | transferrin elevated (the body "catches" iron) |
| Inflammation, liver disease | transferrin reduced |
| Pregnancy, estrogen | physiologically elevated |
What an elevated level means
Elevated transferrin is a classic sign of iron deficiency: the body ramps up the transport protein, trying to make more efficient use of its scanty stores. Ferritin and transferrin saturation are usually reduced at the same time.
Physiologically, transferrin rises in pregnancy and with estrogen use.
What a low level means
Reduced transferrin occurs in several conditions.
Inflammation and chronic disease — transferrin is a "negative acute-phase protein" and falls (anemia of chronic disease). Liver disease — it is synthesized there, so with liver failure there is less of it. Protein deficiency and iron overload — also lower transferrin.
How the test is done
Transferrin is measured from venous blood, preferably in the morning fasting (iron has a daily rhythm). It is almost always interpreted as part of the "iron profile": serum iron, ferritin, TIBC and transferrin saturation — each marker on its own can be misread.
What affects the value
- Iron deficiency — raises transferrin.
- Inflammation and infections — lower it (a negative acute-phase protein).
- Liver disease — reduces synthesis.
- Pregnancy, estrogen and oral contraceptives — raise it.
- Dietary protein deficiency — lowers it.
- Iron overload — lowers it.
Assess iron deficiency
Transferrin is part of the iron profile; assess your risk of iron deficiency:
Frequently asked questions
How does transferrin differ from ferritin?
Ferritin is the iron store (how much is in the warehouse), while transferrin is the transport (how many "trucks" carry it). In iron deficiency the store (ferritin) falls while the transport (transferrin) rises. That is why they are looked at together — they complement the picture.
Why is transferrin high but iron low?
This is a typical picture of iron deficiency: the body ramps up transferrin to catch as much of the scarce iron as possible. The diagnosis is confirmed by low ferritin and low transferrin saturation.
Is low transferrin dangerous?
A fall by itself more often reflects inflammation, liver disease or protein deficiency than an iron problem. It should be interpreted in the context of the whole iron profile and overall condition, not in isolation.
Related terms
Sources
- Iron-Binding Capacity (TIBC/transferrin) — StatPearls (NCBI)
- MedlinePlus (NIH) — Transferrin Test
- MedlinePlus (NIH) — Iron Tests