What is the normal transferrin saturation percentage?

Normal Transferrin Saturation Percentage

Normal transferrin saturation (TSAT) is ≥16% in adults, with values varying by age and sex. 1

Age-Related Normal Values

Transferrin saturation varies significantly across the lifespan:

• Neonates: Highest TSAT values 1
• 4 months of age: TSAT decreases to lowest point 1
• Childhood through adolescence: TSAT gradually increases until reaching adult levels 1
• Adults: TSAT stabilizes at higher values compared to children 2, 3

Sex-Related Differences in Adults

Adult women have lower normal TSAT values than men:

• Women show lower transferrin saturation centiles compared to males when using the same reference ranges 4
• Serum ferritin (but not TSAT) in healthy women increases sharply during menopause 4

Clinical Thresholds for Iron Deficiency

TSAT <16% in adults is the established cutoff for confirming iron deficiency 1, though this threshold has important limitations:

• Among nonpregnant women of childbearing age, TSAT <16% has only 20% sensitivity but 93% specificity for iron deficiency (defined by absent bone marrow iron) 1
• In children aged 0.5-12 years, TSAT <16% constitutes evidence of iron deficiency only when combined with anemia and low mean corpuscular volume 3

Context-Specific Thresholds

Different clinical contexts use varying TSAT cutoffs:

• Chronic kidney disease: TSAT <20% defines absolute iron deficiency 1
• Heart failure: TSAT <20% with ferritin 100-299 ng/mL defines functional iron deficiency 1
• Cancer/chemotherapy: TSAT <20% with ferritin <800 ng/mL indicates functional iron deficiency 1
• General screening: Population studies use cutoffs ranging from >45% to >62% to identify elevated TSAT 5

Important Clinical Caveats

Multiple factors cause significant TSAT variability:

• Diurnal variation: TSAT rises in morning, falls at night—larger variation than hemoglobin or hematocrit 1
• Meal effects: Serum iron (and thus TSAT) increases after each meal 1
• Day-to-day variation: Greater within-individual variation than hemoglobin 1
• Inflammation/infection: Decreases serum iron and TSAT independent of iron stores 1
• Chronic diseases: Malignancies, liver disease, nephrotic syndrome, malnutrition lower TIBC and affect TSAT 1
• Hormonal factors: Oral contraceptives and pregnancy raise TIBC and affect TSAT 1

Practical Interpretation Algorithm

When evaluating TSAT results:

1. TSAT ≥20%: Generally indicates adequate iron availability for erythropoiesis in most clinical contexts 1

2. TSAT <20%: Suggests iron-restricted erythropoiesis, but must interpret with ferritin 1:

   • If ferritin <100 ng/mL: Absolute iron deficiency 1
   • If ferritin 100-800 ng/mL: Functional iron deficiency 1
   • If ferritin >800 ng/mL: Consider inflammatory block 1

3. TSAT <16%: Confirms iron deficiency in adults when combined with appropriate clinical context 1

TSAT is less sensitive than serum ferritin for detecting depleted iron stores because TSAT changes occur after iron stores are already depleted, making it an indicator of iron-deficient erythropoiesis rather than early iron depletion 1.