What is the clinical interpretation of an iron level of 200, TIBC of 405, percent saturation of 49, and a ferritin level of 20?

Iron Studies Interpretation: Functional Iron Deficiency

These laboratory values indicate functional iron deficiency—a state where total body iron stores are depleted (ferritin 20 ng/mL) despite adequate circulating iron availability (transferrin saturation 49%), creating a paradoxical pattern that requires iron supplementation. 1

Understanding the Paradox

Your iron panel shows a contradictory pattern that requires careful interpretation:

• Serum iron 200 μg/dL: Elevated circulating iron 1
• TIBC 405 μg/dL: Normal to slightly elevated binding capacity 1
• Transferrin saturation 49%: Near the upper threshold of normal, indicating approximately half of transferrin binding sites are occupied 1
• Ferritin 20 ng/mL: Severely depleted iron stores 1, 2

Clinical Significance

The ferritin of 20 ng/mL is the critical finding here—this represents true iron store depletion regardless of the elevated transferrin saturation. 2, 3

• In healthy adults, ferritin <30 ng/mL indicates absolute iron deficiency with very high specificity (98%) 2
• Normal ferritin ranges are 20-300 μg/L in healthy adults, placing your value at the extreme lower end 4
• The elevated transferrin saturation (49%) does not exclude iron deficiency when ferritin is this low 1

Differential Diagnosis Considerations

This pattern suggests one of three scenarios:

1. Recent iron supplementation or transfusion: The elevated serum iron and TSAT may reflect recent oral/IV iron intake while stores remain depleted 1

2. Hemolysis or ineffective erythropoiesis: Conditions like thalassemia can create paradoxical iron metabolism with low ferritin despite elevated TSAT 5

3. Timing of laboratory draw: Serum iron has diurnal variation, and a single elevated value may not reflect true iron status 1

Recommended Evaluation

Before initiating treatment, investigate the following:

• Blood loss sources: Gastrointestinal bleeding (especially if >50 years old, as 9% have GI malignancy), menorrhagia, or other occult bleeding 3
• Inflammatory conditions: Ferritin is an acute-phase reactant; however, inflammation typically elevates ferritin, making this less likely here 1, 2
• Hemoglobinopathy screening: If family history or ethnicity suggests thalassemia, obtain hemoglobin electrophoresis and soluble transferrin receptor (sTfR) 5
• Medication history: Confirm whether recent iron supplementation was taken before the blood draw 1

Management Approach

Iron supplementation is indicated based on the ferritin of 20 ng/mL:

• Oral iron trial: In otherwise healthy adults without malabsorption, initiate oral iron supplementation and recheck hemoglobin in 1 month—expect a 1-2 g/dL increase if absorption is adequate 3
• If hemoglobin fails to rise: Consider malabsorption, ongoing blood loss, or need for endoscopic evaluation (colonoscopy if >50 years) 3
• Target ferritin: Aim for ferritin >50 ng/mL to replete stores 1
• Monitor TSAT: The transferrin saturation should not be chronically maintained ≥50% to avoid iron overload risk 5

Critical Pitfalls to Avoid

• Do not dismiss iron deficiency based on elevated TSAT alone—ferritin is the definitive marker of iron stores 1, 2
• Do not over-supplement—recheck ferritin after 4-8 weeks of supplementation to avoid overshoot into iron overload (ferritin >500 ng/mL) 1, 5
• Do not ignore the need for source investigation—iron deficiency in adults warrants evaluation for occult bleeding 3