Iron Studies Explained: Serum Iron, TIBC, Transferrin and Saturation
Iron studies go beyond ferritin — they reveal the difference between iron deficiency, anaemia of inflammation and iron overload. Learn the pattern each condition produces.
A full iron panel measures serum iron (60–170 µg/dL), total iron binding capacity or TIBC (240–450 µg/dL) and calculates transferrin saturation (20–50%). In iron deficiency: iron LOW, TIBC HIGH, saturation < 15%. In anaemia of chronic disease: iron LOW, TIBC LOW, saturation normal or low. In haemochromatosis: iron HIGH, TIBC LOW, saturation > 45%.
Iron studies interpret three interdependent measurements. Serum iron is the amount currently in transit on transferrin; it varies diurnally by 20–30% (peak in morning). TIBC reflects the amount of transferrin available for iron transport — it rises in iron deficiency (the body upregulates transferrin) and falls in inflammation or malnutrition. Transferrin saturation = (iron ÷ TIBC) × 100; it is the most useful single derived value. Saturation < 15% strongly suggests iron deficiency; > 45% suggests iron overload. Always interpret iron studies with ferritin — the pattern quartet clinches the diagnosis.
- Serum iron
- 60–170 µg/dL (11–30 µmol/L)
- TIBC
- 240–450 µg/dL
- Transferrin saturation
- 20–50%
- Iron deficiency saturation
- < 15%
- Haemochromatosis saturation
- > 45%
What each measurement means
Serum iron: the concentration of iron circulating on transferrin at the moment of the draw. It varies diurnally (highest early morning) and after meals — draw fasting in the morning for consistency.
TIBC: total iron binding capacity — a measure of the transferrin protein's carrying capacity. Iron deficiency triggers the liver to make more transferrin (higher TIBC); inflammation or malnutrition drops production (lower TIBC).
Transferrin saturation: the percentage of transferrin sites currently occupied by iron. This is the most physiologically meaningful number because it combines supply (iron) with capacity (TIBC).
Iron panel patterns
| Condition | Iron | TIBC | Saturation | Ferritin |
|---|---|---|---|---|
| Iron deficiency | Low | High | < 15% | Low |
| Anaemia of chronic disease | Low | Low | Normal or low | Normal or high |
| Iron overload / haemochromatosis | High | Low | > 45% | High |
| Sideroblastic anaemia | High | Normal | High | High |
| Recent iron supplementation | High (transient) | Normal | High | Normal or high |
When to order iron studies vs ferritin alone
Ferritin alone is enough for most iron deficiency screening. Order the full iron panel when: (1) inflammation is present and ferritin is unreliable; (2) diagnosing haemochromatosis (saturation is the key first-line marker); (3) atypical anaemia patterns where the pattern quartet clarifies which mechanism is dominant.
What causes each pattern
Iron deficiency: menstrual loss, GI bleeding, dietary shortfall, malabsorption (coeliac, IBD, gastric bypass), pregnancy demands.
Anaemia of chronic disease: rheumatoid arthritis, chronic infections, malignancy, CKD, chronic liver disease. Hepcidin is elevated, trapping iron in macrophages — supply low, capacity low.
Iron overload: hereditary haemochromatosis (HFE C282Y homozygous most common), transfusion-dependent anaemia, chronic liver disease.
- Transferrin saturation > 45% with elevated ferritin — screen for haemochromatosis.
- Iron studies suggest deficiency in a man or postmenopausal woman — always assess GI bleeding.
- Bronze skin, joint pain, new diabetes with elevated iron studies — iron overload workup.
- Iron deficiency plus GI symptoms (weight loss, altered bowel habit) — urgent GI referral.
Iron panel interpretation walk-through
- 1Iron low, TIBC high, saturation < 15%?Iron deficiency. Investigate cause (menstrual, GI, dietary). Replace iron.
- 2Iron low, TIBC low, saturation normal?Anaemia of chronic disease. Investigate underlying inflammatory or renal disease. Iron replacement is usually ineffective without treating the underlying cause.
- 3Iron high, TIBC low, saturation > 45%?Iron overload workup. HFE gene testing, hepatology referral. Consider phlebotomy.
- 4Mixed picture with inflammation?Iron deficiency can be masked. Check soluble transferrin receptor or trial iron supplementation with follow-up.
Related questions people ask
- What does high ferritin low iron mean?
- Is transferrin saturation more accurate than ferritin?
- What is haemochromatosis?
- Why is TIBC high in iron deficiency?
- How do I read a CBC after iron studies?
- When is IV iron indicated?
- How does inflammation affect iron studies?
Frequently asked questions
- Pattern reading (iron + TIBC + saturation + ferritin) beats any single value.
- Iron deficiency: iron low, TIBC high, saturation < 15%, ferritin low.
- Anaemia of chronic disease: iron low, TIBC low, saturation normal, ferritin high.
- Haemochromatosis: saturation > 45%, ferritin high.
- Draw fasting morning; pause supplements 24–48 h before.
- Ferritin is the first-line test — full panel adds value when the picture is unclear.
References
3 sources- BSHIron Deficiency Guidelines
UK haematology guideline.
b-s-h.org.uk
- AASLDHereditary Hemochromatosis
US iron overload guideline.
aasld.org
- WHOAssessing Iron Status
International iron status framework.
who.int
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