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HematologyTSAT

Transferrin Saturation Calculator (TSAT)

Calculate TSAT from same-assessment serum iron and laboratory-reported TIBC with exact unit normalization.

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Formula and medical content are based on the references listed on this page. See sources, About, and Sources and Review Process.

Serum iron

Use the serum iron value from the same laboratory assessment as TIBC; zero is accepted mathematically.

Match the unit printed beside this result.

Total iron-binding capacity (TIBC)

Use the positive TIBC formally reported by the laboratory from the same assessment.

Match the unit printed beside this result.

Laboratory-source guidance

Use serum iron and TIBC from the same laboratory assessment when interpreting TSAT. Enter the TIBC value reported by the laboratory; that value may have been measured or calculated within the laboratory's own method or information system. QuickMedCalc cannot verify specimen or report provenance, or how TIBC was derived, and it does not calculate TIBC from transferrin or UIBC.

TSAT result will appear here

Enter serum iron and laboratory-reported TIBC from the same assessment. The calculator reports a neutral transferrin-saturation percentage and does not label it low, normal, or high.

About

Transferrin saturation (TSAT), also called iron saturation, is a calculated percentage using serum iron and laboratory-reported TIBC from the same assessment. It is not ferritin, a direct measurement of body iron stores, a diagnosis, or a treatment decision. [1, 2]

Formula

TSAT (%) = serum iron ÷ TIBC × 100. Serum iron and TIBC are normalized to the same concentration unit before division. [1, 2]

Interpretation

What does TSAT measure?

TSAT expresses serum iron as a percentage of the reported TIBC. It does not directly measure ferritin, body iron stores, transferrin, UIBC, or iron overload. Those are separate measurements or clinical questions. [2, 4]

Is there one universal TSAT range?

No. Interpretation depends on the reporting laboratory, assay, population, collection conditions, ferritin, inflammation, and the clinical pathway. This calculator therefore reports the arithmetic without a low, normal, or high category. [4, 7]

Worked arithmetic example

For same-assessment serum iron 100 µg/dL and reported TIBC 300 µg/dL, the calculator returns 100 µg/dL ÷ 300 µg/dL × 100 ≈ 33.3%. This example demonstrates the calculation only; it does not assign a category.

Why this calculator uses laboratory-reported TIBC

A laboratory may measure TIBC directly or derive it within its validated method. Enter the TIBC formally reported with the serum iron result. This calculator does not calculate TIBC from transferrin or UIBC and does not apply a generic local conversion. [2, 7]

What can a lower TSAT mean?

A lower value can occur when less circulating iron is available relative to binding capacity, but TSAT alone does not diagnose iron deficiency. In CKD-specific KDIGO 2026 terminology, TSAT below 20% appears in descriptions of systemic iron deficiency and iron-restricted erythropoiesis only with ferritin and CKD context. That source-specific framework is not a universal cutoff and is not applied to this result. [4, 6]

What can a higher TSAT mean?

A higher value can prompt evaluation in an appropriate pathway, but it does not diagnose iron overload. EASL 2022 uses TSAT greater than 45% in females and greater than 50% in males in a haemochromatosis pathway that also depends on ferritin, sex/menopause, HFE genotype, and sometimes MRI or biopsy. This calculator does not collect or apply those criteria. [5]

TSAT and ferritin answer different questions

TSAT is a calculated circulating iron-to-binding-capacity percentage. Ferritin is a separate marker used when assessing iron stores and is affected by inflammation and other clinical conditions. Current iron-assessment pathways interpret these measurements together rather than treating TSAT as a substitute for ferritin. [4, 6]

Collection timing and repeat comparison

Serum iron varies within and between days and with fasting duration. Follow the reporting laboratory’s preparation instructions and, when serial results are compared, consider whether collection conditions were comparable. The evidence does not support adding one universal fasting-hours rule to this calculator. [3]

Limits of this result

This page calculates TSAT only. It does not diagnose or exclude deficiency, overload, haemochromatosis, inflammation, liver or kidney disease; choose testing, referral, iron, phlebotomy, dose, or treatment; or replace the source laboratory report and clinical assessment. [4, 5, 6]

References

  1. Ramsay WN. The determination of the total iron-binding capacity of serum. Clin Chim Acta. 1957;2(3):221–226. PMID 13461309. DOI 10.1016/0009-8981(57)90106-7.
  2. Kasvosve I, Delanghe J. Total iron binding capacity and transferrin concentration in the assessment of iron status. Clin Chem Lab Med. 2002;40(10):1014–1018. PMID 12476940. DOI 10.1515/CCLM.2002.176.
  3. Nguyen LT, et al. Influence of diurnal variation and fasting on serum iron concentrations in a community-based population. Clin Biochem. 2017;50(18):1237–1242. PMID 28947322. DOI 10.1016/j.clinbiochem.2017.09.018.
  4. Fletcher A, Forbes A, Svenson N, Thomas DW. Guideline for the laboratory diagnosis of iron deficiency in adults (excluding pregnancy) and children. Br J Haematol. 2022;196(3):523–529. PMID 34693519. DOI 10.1111/bjh.17900.
  5. European Association for the Study of the Liver. EASL Clinical Practice Guidelines on haemochromatosis. J Hepatol. 2022;77(2):479–502. PMID 35662478. DOI 10.1016/j.jhep.2022.03.033.
  6. KDIGO Anemia Work Group. KDIGO 2026 Clinical Practice Guideline for the Management of Anemia in Chronic Kidney Disease. Kidney Int. 2026;109(1S):S1–S99. PMID 41485812. DOI 10.1016/j.kint.2025.06.006.
  7. Mayo Clinic Laboratories. Iron and Total Iron-Binding Capacity, Serum. Laboratory test catalog. Accessed September 4, 2026.

FAQ

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Disclaimer

Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.