Transferrin and saturation: what these iron values say

Besides ferritin and haemoglobin, an iron work-up often shows two other values: transferrin and transferrin saturation. They do not tell how much iron you store, but how iron is transported through your blood (Camaschella 2019). I think they are unfairly overlooked, because they help spot a misleading ferritin.

This article expands on the overview about anaemia and iron deficiency, looking at the transport side of iron.

What is transferrin?

Transferrin is the protein that carries iron through your blood, a bit like a bus that picks up iron and delivers it where needed. With a deficiency your body often makes more transferrin, as if adding buses to spread the scarce iron. So a deficiency often shows a raised transferrin while there is little iron to carry.

What is transferrin saturation?

Saturation shows how much of your transport is actually filled with iron: the percentage of seats taken on those buses. Many buses with few passengers means low saturation, which fits a deficiency. Overfull buses mean high saturation, which can fit an excess.

Why are these values useful next to ferritin?

Ferritin is sensitive, but it rises with inflammation or hard exercise, so a normal or high ferritin can mask low iron. Then transferrin and saturation add grip. The ferritin numbers are at the ferritin level explained.

Which values belong together?

A complete iron picture usually combines ferritin, iron, transferrin and saturation, with haemoglobin to spot anaemia. A broader iron test with ferritin and more often gives more insight than one number. Thinking of the high side? See too much iron and haemochromatosis.

What can you do?

To measure transport and store together, you can have your iron status tested at Vitalcheck, and discuss abnormal values with your GP. A practical tip: draw iron values at a quiet moment, not right after an infection or hard training.

References

• Camaschella C. Iron deficiency. Blood. 2019. PMID: 30401704.
• Pasricha SR, et al. Iron deficiency. Lancet. 2021. PMID: 33285139.
• NHG-Standaard Anemie. Dutch College of General Practitioners.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.