Transferrin Saturation Calculator (TSAT)
Calculate TSAT from same-assessment serum iron and laboratory-reported TIBC with exact unit normalization.
Content updated: View sources
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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.
About
Formula
Interpretation
What the result represents
A calculated percentage of laboratory-reported iron-binding capacity occupied by serum iron. It is not a direct measurement of total-body iron stores.
Input units
Each value may use µg/dL or µmol/L. The page independently normalizes both values with 1 µmol/L = 5.5845 µg/dL before division. This page does not estimate TIBC from transferrin.
TIBC source identity
Use the TIBC formally reported on the laboratory report. A laboratory may report a directly measured TIBC or calculate TIBC from a transferrin result within its own method or laboratory information system. You do not need to know the internal method for this page; do not calculate a replacement yourself from transferrin with a generic conversion factor. [8]
Worked example — not a category
Serum iron 100 µg/dL and TIBC 300 µg/dL gives 100 ÷ 300 × 100 ≈ 33.3%.
Applicable population
Laboratory arithmetic for a person whose same-assessment serum iron and laboratory-reported TIBC are available. Age, pregnancy, CKD, liver disease, inflammation, and iron-overload pathways require their own reference intervals and clinical criteria.
Children require age-specific reference intervals: the CALIPER cohort used a particular analytical platform and reported sex stratification during adolescence, so laboratories must verify their own population and method. Serum iron, TIBC, and TSAT can also change across pregnancy and postpartum stages; the cited healthy Chinese pregnancy cohort is not a dynamic pregnancy interval for this result.
Static pathway examples — not calculated
| Context | Guideline-specific use | Limit |
|---|---|---|
| EASL 2022 haemochromatosis | Uses elevated TSAT examples of >45% in females and >50% in males. In the p.Cys282Tyr/HFE homozygous provisional iron-overload context, the paired ferritin examples are >200 ng/mL in females and >300 ng/mL in males or postmenopausal women. [6] | These are pathway-specific examples requiring ferritin, sex/menopause and genotype context; other genotypes may require MRI or biopsy evidence. They are not a universal TSAT category. [6] |
| KDIGO 2026 anemia in CKD | In the non-hemodialysis/peritoneal-dialysis pathway, an iron-deficiency example is ferritin <100 ng/mL and TSAT <40%, or ferritin 100 to <300 ng/mL and TSAT <25%. For CKD G5 receiving hemodialysis, an iron initiation context uses ferritin ≤500 ng/mL and TSAT ≤30%; routine iron may reasonably be withheld if ferritin >700 ng/mL or TSAT ≥40%. [7] | These CKD-, modality-, ferritin-, and anemia-dependent examples are not general-population categories. This page does not apply them or choose iron therapy. [7] |
| WHO 2020 ferritin guidance | Centers ferritin and accounts for inflammation and population context. [5] | TSAT alone does not establish deficiency or overload. |
Interpretation limitations
Interpret the source laboratory method and interval, ferritin, inflammation, liver status, CKD, transfusion and iron exposure, collection timing, fasting duration, and the applicable clinical pathway. A single calculated TSAT cannot diagnose or exclude a disorder or select testing or treatment.
References
- 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.
- 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.
- Dale JC, Burritt MF, Zinsmeister AR. Diurnal variation of serum iron, iron-binding capacity, transferrin saturation, and ferritin levels. Am J Clin Pathol. 2002;117(5):802–808. PMID 12090432. DOI 10.1309/2YT4-CMP3-KYW7-9RK1.
- 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.
- World Health Organization. WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations. 2020. ISBN 978-92-4-000012-4.
- 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.
- 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.
- Mayo Clinic Laboratories. TIBC — Overview: Total Iron Binding Capacity, Serum. Test 2501. Laboratory method example accessed 2026-08-17.
- Higgins V, Chan MK, Adeli K. Pediatric Reference Intervals for Transferrin Saturation in the CALIPER Cohort of Healthy Children and Adolescents. EJIFCC. 2017;28(1):77–84. PMID 28439220. PMCID PMC5387701.
- Yu F, Zhou W, Yin M, Hu Z. Prospective and Longitudinal Study of Iron Metabolism Indicators During Normal Pregnancy in Chinese Women. Clin Lab. 2019;65(5):743–751. PMID 31115223. DOI 10.7754/Clin.Lab.2018.180928.
FAQ
TSAT is serum iron divided by total iron-binding capacity, multiplied by 100. Both values are independently normalized to the same iron concentration unit before division.
It is a calculated percentage of the laboratory-reported iron-binding capacity occupied by serum iron. It is not a direct measure of total-body iron stores.
Yes. Combining unrelated collection times or clinical states can create a ratio that does not describe one laboratory assessment.
Serum iron and TIBC may each use µg/dL or µmol/L. The page uses the exact iron conversion 1 µmol/L = 5.5845 µg/dL and allows mixed units.
No. Enter the TIBC formally reported by the laboratory. That reported value may be directly measured or calculated by the laboratory from transferrin under its own method; you do not need to know the laboratory's internal method. Do not calculate a replacement yourself from transferrin with a generic conversion factor, and this page does not add a transferrin input.
Sources: [8]
Zero is accepted mathematically and gives TSAT 0.0% when TIBC is positive. The source result and assay context still require review.
TIBC is the denominator. A zero or negative denominator cannot produce a valid transferrin-saturation calculation.
The arithmetic can exceed 100% when submitted serum iron exceeds TIBC. The page reports that calculation neutrally; it does not validate the specimen, assay, or diagnosis.
No. Ferritin, inflammation, blood counts, symptoms, population, and the applicable pathway matter. WHO guidance centers ferritin and its inflammatory context rather than using TSAT alone.
No. EASL uses source-specific examples of TSAT >45% in females and >50% in males; in the p.Cys282Tyr/HFE homozygous provisional iron-overload context, the paired ferritin examples are >200 ng/mL in females and >300 ng/mL in males or postmenopausal women. Other genotypes may require MRI or biopsy evidence. These are not universal categories and this page does not apply them dynamically.
Sources: [6]
KDIGO 2026 uses TSAT with ferritin and CKD or dialysis context. Examples include ferritin <100 ng/mL with TSAT <40%, or ferritin 100 to <300 ng/mL with TSAT <25% in a non-hemodialysis pathway; in CKD G5 receiving hemodialysis, an iron-initiation context uses ferritin ≤500 ng/mL with TSAT ≤30%, while routine iron may reasonably be withheld if ferritin >700 ng/mL or TSAT ≥40%. These are CKD-specific management contexts, not universal categories, and this page does not choose treatment.
Sources: [7]
Serum iron varies within and between days and can be influenced by meals and fasting duration. Interpret the result with the collection conditions and laboratory instructions.
Yes. Inflammation, liver function, transferrin concentration, nutrition, and assay method can alter iron markers and their relationship.
Not automatically. CALIPER reported age-specific pediatric transferrin-saturation intervals, with sex stratification during adolescence, on a specific analytical platform. Laboratories should validate local population and method performance; this page does not apply a pediatric interval to a result.
It can. Serum iron, TIBC, and TSAT vary across pregnancy and postpartum stages. A prospective healthy Chinese pregnancy cohort is population-specific, so this page does not apply a pregnancy interval or make a pregnancy diagnosis or treatment decision.
Yes. Recent iron exposure, transfusion, and treatment timing can change serum iron and TSAT. The page does not infer treatment response or timing.
No. It cannot order ferritin, genetic testing, imaging, biopsy, referral, iron, phlebotomy, medication, dose, or another intervention.
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Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.