Iron Deficiency Calculator: TSAT, Ferritin and Ganzoni Deficit

TSAT, a CRP-aware ferritin reference threshold and the arithmetic Ganzoni model. Biomarker patterns are not diagnoses.

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Result

Interpretation: Pattern not classified; these thresholds do not exclude a diagnosis
Transferrin saturation (TSAT): 12.5 %
Ferritin threshold for deficiency: 15 µg/L
Total iron deficit (Ganzoni): Hb is not below threshold — calculation not shown
TIBC used: 72.0 µmol/L
Serum iron: 9.0 µmol/L

WHO 2020; Ganzoni 1970 formula and Venofer instructions. Reference ranges are population benchmarks from the cited sources. Laboratories use their own ranges, and interpretation depends on clinical context: discuss the result with your physician.

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How it is calculated

TSAT is serum iron divided by TIBC in matching units. TIBC derived from transferrin is approximate. Ferritin comparison uses WHO 2020 references: 15 µg/L without inflammation and 70 µg/L at CRP > 5 mg/L. Diseases and clinical context may require different thresholds. The pattern does not establish the cause of anemia. Ganzoni is shown below Hb 120 g/L in women or 130 g/L in men, using a fixed target of 150 g/L and 500 mg stores, only at weight ≥ 35 kg.

Formula

TSAT (%) = Serum iron / TIBC × 100 TIBC (µmol/L) ≈ Transferrin (g/L) × 25.1 Iron deficit (mg, Ganzoni) = Weight (kg) × (Target Hb − Hb, g/dL) × 2.4 + Stores (500 mg at weight ≥ 35 kg) Conversion: iron µg/dL × 0.179 = µmol/L; Hb g/L / 10 = g/dL

Limits of the method

For nonpregnant adults. Enter measured CRP; an unknown test must not be treated as zero. Ferritin and TSAT depend on inflammation, laboratory methods and recent treatment. Ganzoni does not select an administration route, product, dose per administration or treatment duration.

Sources of the method

This calculation is for reference only and is not medical advice, a diagnosis or a prescription. If you have a medical condition, are pregnant, take medication or have any doubts, discuss the result with a physician or a qualified nutrition professional.

How to assess iron status from labs

Prepare your laboratory results

Use results from one laboratory assessment: ferritin, iron, TIBC or transferrin, Hb and CRP. Ask the laboratory about test preparation.

Add CRP

At measured CRP above 5 mg/L, the ferritin reference changes from 15 to 70 µg/L. This does not eliminate all interpretive uncertainty.

Discuss the biomarker pattern

Low Hb is not always caused by iron deficiency, and absence of a flag does not exclude deficiency. Interpret results with symptoms and clinical context.

Iron status worked examples

Low TSATTSAT 12.5%

Woman 62 kg: ferritin 18, iron 9, TIBC 72 µmol/L, Hb 124 g/L

TSAT = 9 / 72 × 100 = 12.5%. Ferritin 18 is above the reference threshold of 15, but this does not exclude clinical deficiency; context needs assessment.

The calculator does not prescribe iron.

Low Hb and ferritinDeficit 1,126 mg

Woman 58 kg: ferritin 8, iron 6, TIBC 80, Hb 105 g/L

TSAT 7.5%. Model: 58 × (15 − 10.5) × 2.4 + 500 = 1126.4 mg, rounded to 1126 mg. A clinician evaluates the cause of low Hb.

This is a total model estimate, not administration instructions.

Low TSAT with inflammationTSAT 15.6%

Man 82 kg: ferritin 180, iron 7, TIBC 45, Hb 118, CRP 22 mg/L

Low TSAT with elevated CRP needs assessment alongside ferritin and Hb. The pattern alone cannot select oral or intravenous treatment.

The source of inflammation must be found; IV iron is a physician’s decision.

Why "normal hemoglobin" does not rule out iron deficiency

The body protects hemoglobin to the last: stores in the liver and macrophages are used first (ferritin falls), then iron delivery to the marrow declines (TSAT falls), and only when compensation is exhausted does hemoglobin drop. Up to 30% of women of reproductive age have iron deficiency without anemia — with fatigue, reduced endurance, brittle hair and nails, yet a "normal" blood count. That is why WHO recommends looking at ferritin, not just hemoglobin.

Ferritin in inflammation: an interpretation trap

Ferritin is an acute-phase protein and may rise with inflammation. WHO 2020 allows a 70 µg/L threshold in adults with inflammation, with low certainty of evidence. Disease-specific thresholds should not be applied to all visitors.

Biomarker patterns: reference table

Stage	Ferritin	TSAT	Hemoglobin
Selected thresholds not crossed	≥ 15 µg/L (≥ 70 with inflammation)	20–45%	Not below threshold
Ferritin below threshold	< 15 µg/L	≥ 20%	Not below threshold
Low ferritin and TSAT	< 15 µg/L	< 20%	Not below threshold
Low ferritin and Hb	< 15 µg/L	< 20%	< 120 g/L (women) / < 130 g/L (men)
Low TSAT with elevated CRP	Not below threshold or elevated	< 20%	Reduced, CRP elevated

Thresholds per WHO 2020 and Camaschella 2015; limits differ in pregnancy and children.

Frequently asked questions

What is a normal ferritin?

WHO 2020 uses < 15 µg/L in adults without inflammation and allows < 70 µg/L with inflammation. Disease-specific clinical guidance may differ; a result above the threshold does not exclude deficiency.

What is transferrin saturation and why is it better than serum iron?

Serum iron swings widely during the day and with food. TSAT — iron divided by total iron-binding capacity — shows what share of transport sites is occupied and is more stable. Below 20% means too little iron for blood formation.

Can TIBC be calculated from transferrin?

Approximately, yes: TIBC (µmol/L) ≈ transferrin (g/L) × 25.1, or in µg/dL ≈ transferrin (mg/dL) × 1.4. The calculator does this automatically in "Transferrin" mode.

What is the Ganzoni formula for?

The model estimates total iron for a selected target Hb and iron stores. It does not directly translate into a tablet course or a safe single intravenous dose.

How fast does ferritin recover?

Timing depends on the cause, treatment, absorption and ongoing losses. A single calculation cannot predict recovery time or select follow-up timing.

Why is iron given every other day?

A single iron dose raises hepcidin for 24–48 hours and blocks absorption of the next. Studies by Moretti and Stoffel showed that alternate-day morning fasting dosing increases total absorption by 30–50% and reduces gastrointestinal side effects.

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What next

Formula breakdowns, biomarker reference ranges and nutrition articles with cited sources are in the NutriFit knowledge base.

Go to the knowledge base