Transferrin Saturation Calculator
Use this transferrin saturation calculator to work out your TSAT from serum iron and TIBC, UIBC or transferrin, in US or SI units.
Updated October 22, 2026
Medical Disclaimer: This calculator gives a general estimate for education only and cannot diagnose a condition. Share your result with your doctor or the clinician who ordered your test, and do not start, stop or change any medicine based on it. Read our full Medical Disclaimer.
How Transferrin Saturation Is Calculated
Transferrin saturation (TSAT) is the share of your blood's iron-carrying protein, transferrin, that is holding iron. It is worked out from two numbers on an iron panel: serum iron and the total amount of iron your transferrin could carry. This calculator does that division for you and shows where the result sits against common lab and guideline cut-offs.
What Transferrin Saturation Measures
Transferrin moves iron through the blood to where it is needed, mainly to make red blood cells. Each transferrin molecule has two iron-binding spots. TSAT shows what percent of those spots are filled at the moment the blood was drawn. It does not measure stored iron, which ferritin reflects, and it does not measure anemia, which hemoglobin shows.
The Formula
TSAT (%) = serum iron ÷ TIBC x 100
TIBC = serum iron + UIBC
TIBC (µmol/L) = transferrin (g/L) x 25.0, which is TIBC (mcg/dL) = transferrin (mg/dL) x 1.396
Iron in mcg/dL x 0.179 = iron in µmol/L
TIBC is total iron-binding capacity, and UIBC is the unused part of it. Labs measure TIBC directly, add serum iron to UIBC, or estimate TIBC from transferrin². The transferrin factor comes from a study of 570 paired samples, which found TIBC in µmol/L is close to 25 times transferrin in g/L, as expected from two iron atoms per molecule⁶. The 0.179 factor comes from the atomic weight of iron (55.845).
How This Calculator Computes Your Result
First choose what your report shows: serum iron with TIBC, with UIBC, or with transferrin. Enter iron, TIBC and UIBC in mcg/dL (also written µg/dL) or µmol/L, and transferrin in mg/dL or g/L. The units can differ between boxes. The tool converts everything to µmol/L, divides, and rounds TSAT to a whole percent, as most labs do. The band is set from that rounded number.
The result shows the sum it used, your iron and TIBC in both units, and the reference range for your sex if you enter it. Sex does not change the result. If iron comes out higher than TIBC (over 100%), the tool asks you to check your numbers.
For example, serum iron of 100 mcg/dL with a TIBC of 300 mcg/dL gives 100 ÷ 300 x 100 = 33%. Using transferrin instead, iron of 180 mcg/dL with transferrin of 250 mg/dL gives a TIBC of 349 mcg/dL and a TSAT of 52%.
What Your Result Means
Your result falls into one of four bands. They use cut-offs from lab references and guidelines, not a diagnosis.
TSAT | Band | What sources say |
Under 16% | Low | People with marked iron deficiency anemia usually have values below 16%⁴ |
16% to 19% | Low end | Below the 20% lower limit many labs use, but within some ranges for women¹ ⁵ |
20% to 44% | Typical | Within common adult reference ranges¹ ⁵ |
45% or higher | High | The level at which liver guidelines look further for iron overload, together with ferritin² ³ |
MedlinePlus lists a normal range of 20% to 50% for men and 15% to 45% for women¹. Labs set their own ranges, so go by the one on your report. European guidelines use sex-specific cut-offs for hemochromatosis testing: above 45% for women with ferritin above 200 µg/L, and above 50% for men with ferritin above 300 µg/L³. The US guideline uses 45% because it catches most people with the common gene type, though it is less specific than higher cut-offs, so it also flags more people who turn out not to have the condition².
How Ferritin Fits With TSAT
TSAT shows iron in transit. Ferritin shows iron in storage. US liver guidelines advise using both together rather than relying on one test². The usual patterns look like this:
TSAT | Ferritin | What it often points to |
Low | Low | Low iron stores. Ferritin under 30 ng/mL (30 µg/L) is specific for iron deficiency⁵ |
Low | Normal or high | Inflammation or long-term illness, where iron is held in storage⁵ |
High | High | The pattern guidelines use to consider testing for hemochromatosis² ³ |
High | Normal | Can be a one-off, for example after recent iron intake¹. A repeat test helps² |
Ferritin rises with infection and inflammation, so a normal ferritin does not always mean iron stores are full⁴. In people with inflammation, a ferritin up to 100 ng/mL can still fit with iron deficiency⁵. In one study of people under 35, a normal ferritin with TSAT under 45% correctly ruled out iron overload 97% of the time².
Timing, Fasting and Why One Result Is Not a Diagnosis
Serum iron moves up and down, so TSAT does too. The WHO notes that both change a lot during the day⁴, and European guidelines say this variability limits how useful TSAT is³. Iron taken shortly before the test can raise the result, which is why labs often ask for a morning or fasting sample¹.
Sources differ on how much timing matters. European guidelines advise a morning sample but say fasting does not improve the test³. The US guideline says fasting is no longer strictly needed, but is still reasonable². A study of 20 healthy adults found no consistent daily pattern: morning iron was higher than afternoon iron in only half of them, and changes from one day to the next were about as large as changes within a day⁷.
Because of this, the US guideline advises confirming a raised TSAT with a second test². High TSAT also has causes other than hemochromatosis, including advanced liver disease, heavy alcohol use and some blood disorders³. Low iron can come from gut bleeding, heavy periods, poor absorption, low dietary iron or pregnancy¹.
Common Mistakes
Mixing units. Iron of 100 mcg/dL is 17.9 µmol/L. Dividing a mcg/dL value by a µmol/L value gives a wrong answer, so pick the unit shown on your report.
Using values from different blood draws. Iron changes from day to day⁷, so use iron and TIBC from the same sample.
Expecting an exact match with a lab that used transferrin. Labs may estimate TIBC with their own method², so a lab's TSAT can differ from ours by a point or two.
TSAT Ranges and Cut-offs by Source
Sources draw the lines in different places. Type a TSAT to see where it falls on each one.
- Below normal range
- Normal range
- Above normal range
- Under the cut-off
- Look further for iron overload
Show data table
| Source | Below normal range | Normal range | Above normal range | Under the cut-off | Look further for iron overload |
|---|---|---|---|---|---|
| MedlinePlus, men | Under 20% | 20% to 50% | Over 50% | – | – |
| MedlinePlus, women | Under 15% | 15% to 45% | Over 45% | – | – |
| US liver guideline | – | – | – | Under 45% | 45% or higher, together with ferritin |
| European guideline, women | – | – | – | 45% or lower | Above 45%, with ferritin above 200 µg/L |
| European guideline, men | – | – | – | 50% or lower | Above 50%, with ferritin above 300 µg/L |
A Note on Accuracy
This calculator does the math exactly, but TSAT is only as reliable as the blood test behind it. Serum iron varies during the day and between days, and recent iron intake can raise it. Guidelines read TSAT together with ferritin and repeat a raised result before drawing conclusions. One result cannot diagnose iron deficiency or hemochromatosis.
Frequently Asked Questions
What is a normal transferrin saturation?
A normal transferrin saturation is about 20% to 50% for men and 15% to 45% for women¹. Your lab's own range is printed on your report and may differ slightly.
What does a high transferrin saturation mean?
A TSAT of 45% or higher is the level at which doctors look further for iron overload, such as hereditary hemochromatosis, usually with ferritin and a repeat test² ³. Recent iron intake, liver disease and heavy alcohol use can also raise it¹ ³.
What does a low transferrin saturation mean?
It means little iron is moving through your blood, which is seen with iron deficiency and also with inflammation⁵. Ferritin helps tell these apart.
Do you need to fast for an accurate transferrin saturation test?
European guidelines say a morning sample is best but fasting does not improve the test³, while US guidelines call fasting reasonable but not required². Iron supplements taken shortly before the test can raise the result¹.
Sources
Serum Iron Test, MedlinePlus, 2026
Diagnosis and Management of Hemochromatosis: 2011 Practice Guideline, Bacon et al., 2011
EASL Clinical Practice Guidelines on Haemochromatosis, European Association for the Study of the Liver, 2022
Iron Deficiency Anaemia: Assessment, Prevention and Control, WHO, 2001
Iron Deficiency Anemia, Merck Manual Professional Version, 2025
The Relation Between Total Iron-Binding Capacity and Transferrin Concentrations, Gambino et al., 1997
Diurnal Variation of Serum Iron, Iron-Binding Capacity, Transferrin Saturation, and Ferritin, Dale et al., 2002