Serum Iron
Serum iron measures iron currently bound to transferrin in circulation. Useful only alongside transferrin/TIBC and ferritin — alone it swings too much to interpret.
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What it measures
Serum iron measures the iron currently in circulation bound to its transport protein transferrin. Levels swing by 30% over a single day (highest in the morning) and react to recent meals, infections and even iron supplements, so a single isolated reading is hard to interpret. Clinically it is used together with transferrin/TIBC and ferritin to compute transferrin saturation (TSAT = iron / TIBC × 100). The combination distinguishes iron-deficiency anaemia (low iron, high TIBC, low ferritin, low TSAT <16%) from anaemia of chronic disease (low iron, low TIBC, normal/high ferritin, normal/low TSAT) and iron overload (high iron, high ferritin, very high TSAT >45%).
What a high value can mean
- Haemochromatosis — hereditary iron overload; TSAT often >45%, ferritin elevated.
- Recent iron supplementation or transfusion — confounds the value for ~24 hours.
- Liver disease — hepatocyte release of iron stores.
- Sideroblastic anaemia — defective haem synthesis; iron accumulates.
What a low value can mean
- Iron-deficiency anaemia — together with low ferritin, low TSAT, high TIBC.
- Anaemia of chronic disease — low iron because of hepcidin-mediated sequestration, NOT depletion; ferritin is normal or high, TIBC is low.
- Recent infection — transient drop.
When to discuss with a doctor
Iron-deficiency vs anaemia-of-chronic-disease cannot be distinguished from serum iron alone — the laboratory needs the full iron panel (ferritin + transferrin/TIBC + TSAT) to make the call. Mediora.AI weighs the panel as a whole; do not treat low serum iron in isolation without ferritin to confirm true deficiency.