Normal TSAT for Non-Hemodialysis Patients
In healthy adults not on hemodialysis, transferrin is normally not more than 50% saturated with iron, meaning normal TSAT ranges up to approximately 50%. 1
Defining Normal vs. Abnormal TSAT
Upper Limit of Normal
- Transferrin saturation above 50% is considered abnormal and may indicate iron overload. 1
- TSAT levels greater than 88% have been associated with transfusional hemosiderosis in dialysis patients, though this represents extreme iron overload. 1
Lower Threshold for Iron Deficiency
- TSAT below 20% indicates iron deficiency in the context of chronic kidney disease and anemia management. 1
- For non-CKD adults, classic iron deficiency is defined by ferritin levels < 25 ng/mL in males and < 11 ng/mL in females, though TSAT < 20% supports this diagnosis. 1
Clinical Context Matters
In Chronic Kidney Disease (Non-Dialysis)
- The Canadian Society of Nephrology and NKF-K/DOQI guidelines recommend maintaining TSAT ≥ 20% in CKD patients with anemia (hemoglobin < 110 g/L). 1
- TSAT < 20% combined with ferritin < 100 ng/mL indicates absolute iron deficiency requiring supplementation. 1
Functional Iron Deficiency
- TSAT < 20% with ferritin 100-700 ng/mL suggests functional iron deficiency, where iron stores exist but cannot be mobilized adequately for erythropoiesis. 1
- This pattern differs from inflammatory iron block, which typically shows abrupt ferritin increases with sudden TSAT drops. 1
Important Caveats
TSAT Interpretation Limitations
- TSAT is most accurate at extreme values—very low TSAT reliably indicates iron deficiency, while very high TSAT indicates iron overload. 1
- Intermediate TSAT values (20-50%) require correlation with ferritin, clinical context, and inflammatory markers for proper interpretation. 1
Impact of Inflammation
- Low TSAT combined with low TIBC suggests chronic inflammation, malnutrition, or liver disease rather than simple iron deficiency. 2
- Inflammatory conditions can lower TSAT by reducing transferrin production (low TIBC) while simultaneously sequestering iron. 2