Normal Iron Saturation Range
The normal range for transferrin saturation (TSAT) is 20-50% in adults. 1
Standard Reference Values
- Normal TSAT: 20-50% in the general adult population 1
- Low TSAT: <20% indicates iron deficiency or iron-deficient erythropoiesis 2, 3
- High TSAT: >50% suggests iron overload or iron-replete status 2
Context-Dependent Thresholds
The interpretation of TSAT varies significantly based on clinical context and underlying conditions:
Chronic Kidney Disease Patients
- Target TSAT ≥20% to support adequate erythropoiesis 2, 4
- TSAT <20% defines absolute iron deficiency when ferritin is also <100 ng/mL 2
- Higher thresholds may be needed to minimize erythropoiesis-stimulating agent requirements 5
Cancer Patients
- TSAT <20% with ferritin <30 ng/mL defines absolute iron deficiency 2
- TSAT 20-50% with ferritin 30-800 ng/mL defines functional iron deficiency 2
- TSAT >50% indicates iron-replete status 2
Pediatric Population
- TSAT <16% in children aged 0.5-12 years constitutes evidence of iron deficiency only when accompanied by anemia and low mean corpuscular volume 6
- Children have significantly lower TSAT values than adults during normal development 6
Critical Interpretation Points
TSAT must be interpreted alongside other iron parameters, particularly ferritin and hemoglobin, rather than in isolation 1, 3:
- TSAT <20% alone does not mandate treatment unless accompanied by low ferritin (<30-100 ng/mL depending on context) or anemia (hemoglobin <110 g/L) 5, 1
- Inflammation falsely lowers TSAT while elevating ferritin, making TSAT the more reliable indicator of iron availability in inflammatory conditions 4
- TSAT >20% does not exclude functional iron deficiency in patients receiving erythropoiesis-stimulating agents who may still respond to iron supplementation 2
Common Pitfalls
- Avoid treating isolated low TSAT (<20%) when ferritin and hemoglobin are normal, as this does not represent clinically significant iron deficiency and iron supplementation may be harmful 5, 1
- Do not rely on TSAT as the sole discriminator between iron-deficient and iron-replete states, as many patients with TSAT >20% may still be functionally iron deficient, while some with TSAT <20% may not require treatment 2
- Consider inflammatory conditions that can cause falsely low TSAT despite adequate iron stores; check C-reactive protein when interpretation is unclear 4