Transferrin Saturation
Percentage of iron-loaded transferrin – key value for iron status and hemochromatosis
Also known as
Definition
Transferrin saturation (TS, also transferrin saturation index or TSAT) indicates what proportion of available transferrin is actually loaded with iron. It is calculated as serum iron divided by total iron-binding capacity (TIBC) × 100. Together with ferritin, it is the key parameter for differentiating iron deficiency (low TS) from iron overload (high TS, suspect hemochromatosis).
| Parameter | Value |
|---|---|
| Unit | % |
| Reference Range | 20–45% | Women tend toward the lower end (15–35%) |
| Optimal Range (lab2go) | 25–40% (lab2go Optimum Zone — sufficient iron without overload; < 20% indicates functional iron deficiency) |
↓ What a low value means
Low transferrin saturation (< 16%) is a sensitive marker for iron-deficient erythropoiesis — the bone marrow is not receiving enough iron for hemoglobin synthesis, even before hemoglobin falls. Combined with low ferritin, it confirms the iron deficiency diagnosis. TS 16–20% with normal ferritin: gray zone — functional iron deficiency possible.
↑ What a high value means
Elevated transferrin saturation (> 45%) is suspicious for iron overload. With TS > 55% + elevated ferritin: initiate genetic hemochromatosis workup (HFE gene test). Secondary causes: frequent transfusions, sideroblastic anemia, dyserythropoietic anemias.
✓ How to optimize this marker
With iron deficiency (low TS): oral iron supplementation (100–200 mg elemental iron daily), clarify the cause (source of bleeding, absorption disorder). Vitamin C 200 mg with iron meals improves absorption. With iron overload (high TS): phlebotomy therapy, low-iron diet.
When to test
Always together with ferritin, serum iron, transferrin, and complete blood count. For anemia workup, hemochromatosis screening (especially Northern Europeans with family history), fasting measurement recommended (daily variation ±30%). Screening in first-degree relatives of hemochromatosis patients.
Frequently asked questions
Why do I need serum iron, transferrin, AND ferritin — isn't one enough? +
Each parameter measures something different: ferritin reflects iron stores (falsified by inflammation), transferrin shows transport capacity, serum iron the currently circulating amount. Transferrin saturation links serum iron with capacity. Only together do they allow differentiation of iron deficiency, inflammatory anemia, and iron overload.
Why should transferrin saturation be measured fasting? +
Serum iron is subject to strong daily variation (rises up to 30% after meals, circadian rhythm peaking in the morning). Transferrin saturation is calculated from serum iron and therefore fluctuates equally. Morning fasting measurement ensures comparability.
What is hereditary hemochromatosis and how is it detected? +
Hereditary hemochromatosis (HFE mutation, especially C282Y homozygosity) is the most common genetic iron overload disease in Northern Europe. First finding: transferrin saturation > 45–55%, often before ferritin rises. Confirmed by HFE gene test. Early symptoms: fatigue, joint pain; late complications: liver cirrhosis, diabetes, heart disease.
Sources
Last Reviewed: May 28, 2026 · sina
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.