How Do You Read Ferritin, Iron, and Transferrin Saturation Results?

Iron tests come as a panel because no single one tells the whole story. Ferritin reflects how much iron you have stored and is the best single test for iron deficiency. Transferrin saturation shows how much iron is in circulation, ready to use. Serum iron on its own varies so much through the day that it means little. Read together, with your haemoglobin, they tell deficiency, overload, and the effects of inflammation apart.

This article is general information, not medical advice. Don’t take iron supplements without knowing your levels: too much iron is harmful.

The Tests

• Serum ferritin: a protein that stores iron; its blood level tracks your iron stores. Low ferritin means depleted stores.
• Serum iron: iron bound to transferrin in the blood at the moment of the draw. It changes with meals and time of day.
• Transferrin and total iron-binding capacity (TIBC): the carrying capacity for iron. Both rise when the body is short of iron.
• Transferrin saturation (TSAT): serum iron divided by TIBC, as a percentage: the share of carrying capacity in use.

The WHO’s Ferritin Thresholds

The World Health Organization’s 2020 guideline on using ferritin to assess iron status sets these thresholds for adults:

Situation	Ferritin indicating iron deficiency
Apparently healthy	Under 15 µg/L
With infection or inflammation	Under 70 µg/L

For iron overload risk in apparently healthy adults, the guideline uses ferritin above 150 µg/L in women and 200 µg/L in men.

Why Inflammation Complicates It

Ferritin is also an acute-phase protein: it rises with infection, inflammation, liver disease, obesity, and heavy drinking, whatever your iron stores. So a “normal” ferritin can hide iron deficiency in someone with inflammation, which is why the WHO uses a higher threshold then, and why labs often measure C-reactive protein alongside it. A high ferritin needs transferrin saturation to interpret: high with high saturation suggests iron overload, such as from haemochromatosis, while high with normal saturation more often reflects inflammation or liver fat.

Typical Patterns

• Iron deficiency: low ferritin, low saturation, high TIBC and transferrin, and, later, low haemoglobin with small red cells.
• Anaemia of inflammation: normal or high ferritin, low saturation, low or normal TIBC.
• Iron overload: high ferritin and high saturation.

Your lab’s printed ranges are the ones that apply to its methods.

Following It in Kaizora

Serum Ferritin, Serum Iron, Transferrin Saturation, Total Iron-Binding Capacity, and Serum Transferrin are lab results on Labs, each with the range its lab printed. A draw’s results share their time and lab, so the panel and your Blood Hemoglobin from the same blood line up. Your Dietary Iron from the Food Log sits on Nutrition; see How to Read a Complete Blood Count.

The Short Version

• Ferritin reflects iron stores; under 15 µg/L means deficiency in healthy adults, by the WHO.
• With inflammation, ferritin reads high; the WHO uses under 70 µg/L then.
• High ferritin with high transferrin saturation suggests iron overload.

Sources

• World Health Organization, WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations (2020).