Iron Panel Blood Test: Serum Iron, TIBC, and Transferrin Saturation Explained
Ferritin alone doesn't tell the whole iron story. The full iron panel — serum iron, TIBC, transferrin saturation, and ferritin together — reveals not just whether you're deficient, but the cause and severity. Here's how to read all four values as a system.
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Get My Score →The Four Iron Panel Values
| Test | Normal Range (US) | What It Measures |
|---|---|---|
| Serum Iron | 60–170 mcg/dL | Iron currently circulating in blood |
| TIBC | 240–450 mcg/dL | Maximum iron blood can carry (transferrin capacity) |
| Transferrin Saturation | 20–50% | Percentage of transferrin carrying iron (serum iron ÷ TIBC × 100) |
| Ferritin | 12–300 ng/mL (men) / 12–150 ng/mL (women) | Iron storage protein — best proxy for body iron stores |
How to Read the Pattern
Iron deficiency: Low serum iron + high TIBC + low transferrin saturation (below 16%) + low ferritin. The high TIBC means the body is producing more transferrin to capture every available iron molecule. This pattern — especially with transferrin saturation below 16% — confirms true iron deficiency and not just anaemia of chronic disease.
Anaemia of chronic disease (ACD): Low serum iron + low or normal TIBC + low or normal transferrin saturation + normal or high ferritin. In ACD, the body sequesters iron to prevent bacteria from using it during illness or inflammation — iron is present but deliberately locked away. Ferritin is an acute phase reactant and rises during inflammation, so it can appear normal or even elevated despite functional iron deficiency.
Iron overload (haemochromatosis): High serum iron + low TIBC + high transferrin saturation (above 45%) + high ferritin. Hereditary haemochromatosis is the most common genetic condition in people of Northern European descent. Transferrin saturation above 45% on two separate tests warrants genetic testing for HFE mutations.
Normal iron stores: All four values within reference range. Transferrin saturation 20–40% is generally considered optimal. A saturation below 16% almost always means functional iron deficiency regardless of ferritin level.
Serum Iron Alone Is Unreliable
Serum iron fluctuates significantly throughout the day — it's highest in the morning and falls by up to 50% in the afternoon. A single low serum iron value alone means little. The full panel, taken fasting in the morning, gives the most reliable picture. This is why doctors order the full panel rather than serum iron in isolation.
Why Ferritin Is the Most Important Iron Marker
Serum iron fluctuates hour to hour with meals and time of day. Ferritin reflects your true iron stores — it is much more stable and clinically meaningful. Low ferritin (below 30 ng/mL) nearly always means iron stores are insufficient, even if serum iron looks normal. Always include ferritin when investigating fatigue or suspected iron deficiency.
When the Iron Panel Is Ordered
Your doctor will typically order an iron panel when your CBC shows low hemoglobin or MCV (to confirm iron deficiency and rule out ACD), when ferritin alone is ambiguous (ferritin can be elevated by inflammation, masking deficiency), when iron overload is suspected (family history of haemochromatosis, unexplained liver disease, elevated ferritin), or when monitoring iron supplementation to confirm stores are being replenished.
Medical Disclaimer
This article is for educational purposes only and does not constitute medical advice. Reference ranges, supplement dosages, and nutritional information mentioned are general educational guidance from published research—not personalised recommendations. Do not use this content to self-diagnose or self-treat any condition. Always consult a qualified healthcare provider before making any changes to your health regimen, medications, or supplements.
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