Normal Transferrin Saturation
Normal transferrin saturation in adults ranges from 20-50%. 1
Standard Reference Ranges
- The normal TSAT range for healthy adults is 20-50%, as established by the American College of Physicians 1
- In healthy individuals without inflammation, TSAT values consistently fall within this range under normal physiological conditions 1
- Normal subjects demonstrate mean transferrin saturation values of approximately 29% in males and 21% in females based on 24-hour monitoring studies 2
Age-Related Variations
- Children between 0.5 and 12 years have significantly lower TSAT values than adults, making age-specific interpretation essential 3
- In pediatric populations aged 0.5-12 years, a TSAT less than 16% should only be considered evidence of iron deficiency when accompanied by anemia and low mean corpuscular volume 3
Clinical Context for Interpretation
Healthy Populations
- TSAT below 16% indicates absolute iron deficiency in healthy individuals without inflammation 1
- Values below 20% suggest a high proportion of vacant iron-binding sites and confirm iron deficiency 1
Inflammatory Conditions
- In patients with chronic inflammatory conditions, TSAT below 20% serves as the diagnostic threshold for iron deficiency 1
- Inflammation and infection can decrease serum iron concentration and artificially lower TSAT values 1
Chronic Kidney Disease Populations
- For hemodialysis patients receiving erythropoiesis-stimulating agents (ESAs), maintaining TSAT greater than 20% is recommended to ensure adequate iron availability for erythropoiesis 4
- Studies demonstrate that targeting TSAT ranges of 30-50% in hemodialysis patients results in lower ESA dose requirements compared to targeting 20-30% 4
Important Physiological Variations
- TSAT exhibits significant diurnal variation, rising in the morning and falling at night 1
- Serum iron concentration increases after each meal, causing fluctuations in TSAT throughout the day 1
- Day-to-day variation in TSAT is greater than that of hemoglobin, with biological variability potentially limiting single-measurement reliability 1, 5
- Within-person biological variability can result in TSAT values crossing diagnostic thresholds on repeated testing, even in the same individual 5
Upper Limit Considerations
- TSAT values exceeding 50% may indicate iron overload conditions 1
- In hemochromatosis patients, TSAT values remain continuously elevated above 69-81% in both treated and untreated individuals 2
- Transferrin is normally not more than 50% saturated with iron in healthy states, ensuring no free iron is available for microbial growth 4
Key Clinical Caveats
- TSAT should never be interpreted in isolation—it must be evaluated alongside serum ferritin for accurate iron status assessment 1
- TSAT is less sensitive to changes in iron stores than serum ferritin concentration 1
- TSAT reflects iron-deficient erythropoiesis rather than total body iron depletion 1
- Laboratory evaluation should not occur within 4 weeks of total dose iron infusion, as circulating iron interferes with the assay 1