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Steps
- Enter ferritin, serum iron, and TIBC or transferrin.
- Add hemoglobin, MCV, and CRP for better context.
- Select fasting and recent iron dose for accuracy notes.
- Press calculate to view results above the form.
- Use downloads to share results with your clinician.
Calculations
Interpretation uses common clinical patterns (educational) and may not match every guideline or lab reference range.
Sample cases
| Case | Ferritin (ng/mL) | Iron (µg/dL) | TIBC (µg/dL) | Hb (g/dL) | CRP (mg/L) | TSAT (%) | Typical pattern |
|---|---|---|---|---|---|---|---|
| A | 10 | 35 | 410 | 10.8 | 2 | 8.5 | Iron deficiency anemia |
| B | 180 | 35 | 250 | 11.2 | 25 | 14 | Inflammation / functional deficiency |
| C | 550 | 190 | 280 | 15.0 | 1 | 67.9 | Iron overload pattern |
These examples are illustrative; real interpretation depends on your lab’s reference ranges and clinical context.
What the panel measures
Ferritin approximates stored iron, while serum iron reflects circulating iron bound to transferrin. TIBC estimates total binding capacity, and transferrin is the main transport protein. TSAT expresses how “full” transferrin is, and UIBC shows remaining capacity. Hemoglobin and MCV add red‑cell context, helping separate early deficiency from anemia. CRP highlights inflammation that can raise ferritin despite low usable iron.
How the calculator derives indices
The calculator reports transferrin saturation as (serum iron ÷ TIBC) × 100. Many laboratories consider roughly 20–45% typical for adults, but ranges vary. UIBC is computed as TIBC − serum iron; a higher UIBC often accompanies deficiency because more binding sites are empty. If TIBC is unavailable, the tool estimates it using TIBC ≈ transferrin × 1.25, and it can reverse that relationship to estimate transferrin.
Interpreting common patterns
A pattern of ferritin below 15–30 ng/mL plus TSAT under 20% is commonly consistent with depleted stores. If hemoglobin is also low, the profile may align with iron deficiency anemia. Microcytosis, fatigue, and restless legs may increase suspicion, yet clinical correlation remains essential overall. When CRP is elevated, ferritin can be normal or high even with restricted delivery; TSAT under 20% with ferritin around or above 100 ng/mL may fit inflammation‑related iron restriction. TSAT above 45% with elevated ferritin can suggest overload, especially if repeated on fasting morning samples.
Factors that shift results
Serum iron changes with time of day and recent supplements; documenting fasting status and a 24‑hour dosing window reduces misinterpretation. Oral iron, recent transfusion, and acute illness can temporarily skew saturation. Chronic kidney disease, liver disease, infection, and inflammatory conditions may lower TSAT and increase ferritin independent of stores. Pregnancy increases iron demand and can lower hemoglobin thresholds, so trend comparison across trimesters is more meaningful than a single value.
When to recheck or escalate
Recheck a morning fasting iron panel when results conflict with symptoms, bleeding risk, or treatment response. If inflammation is suspected, consider adding reticulocyte hemoglobin, soluble transferrin receptor, or repeat CRP for context. If TSAT remains above 45% or ferritin is markedly elevated, discuss confirmatory testing and clinical evaluation promptly with your clinician.
Which inputs are required for a valid result?
Enter ferritin and serum iron, plus either TIBC or transferrin. Hemoglobin, MCV, and CRP are optional but improve interpretation, especially when inflammation or anemia is possible.
Why does the tool ask about fasting and recent iron doses?
Serum iron can rise after supplements and varies during the day. Marking fasting status and recent dosing adds caution notes so saturation is not overestimated from a temporary spike.
What does a low TSAT usually mean?
A TSAT under 20% often indicates limited circulating iron for red‑cell production. It may occur with iron deficiency, inflammation-related restriction, or mixed causes, so ferritin and CRP help clarify.
Can ferritin be “normal” when iron is low?
Yes. Ferritin is an acute‑phase reactant and may increase with infection, inflammation, liver disease, or malignancy. When CRP is elevated, low TSAT with moderate or high ferritin can still reflect iron restriction.
How should I interpret high ferritin and high TSAT?
When both are elevated, an overload pattern is possible. Repeat fasting labs and review alcohol use, liver health, and genetic risk with a clinician before making treatment decisions.
Does this calculator replace medical advice?
No. It summarizes common lab patterns for education. If you have severe symptoms, pregnancy, bleeding, or chronic disease, use the results as a discussion aid with a qualified clinician.
Safety note
Lab patterns can overlap. If you have severe symptoms, pregnancy, known liver disease, or genetic risk for iron overload, get professional medical advice.