Type the transferrin saturation from your iron panel — “% saturation”, “Iron saturation” or “TSAT” — or work it out from the serum iron and TIBC on the same report. You see it against the lines MedlinePlus, Mayo Clinic Laboratories and Cleveland Clinic draw, and what each says at that line. Ferritin, your lab’s own range and your doctor have the last word.
28% is
Inside all three ranges as printed: 28%
Transferrin saturation 28%: inside the 15–45% MedlinePlus prints for women, inside the 14–50% Mayo Clinic Laboratories prints for adults, and inside the 20–50% Cleveland Clinic calls normal.
- Mayo Clinic Laboratories: “Transferrin is generally only 25% to 30% saturated with iron.”
That is inside all three ranges. The range on your own lab report — and your ferritin — are what your doctor reads it against.
Mayo Clinic Laboratories: “However, serum ferritin is a much more sensitive and reliable test for demonstration of iron deficiency.” Check a ferritin result.
What moves it, in the sources’ words
- Mayo Clinic Laboratories: “Iron concentration and percent saturation decrease with iron deficiency and increase when iron is in excess.”
- Mayo Clinic Laboratories: “The intraindividual day-to-day variation of iron and iron saturation is approximately 25% to 30%.”
- Cleveland Clinic: “But one result outside the normal range doesn’t necessarily mean you have a health problem.”
| Source | Women | Men |
|---|---|---|
| MedlinePlus | 15–45% | 20–50% |
| Mayo Clinic Laboratories | 14–50% | 14–50% |
| Cleveland Clinic | 20–50% | 20–50% |
This is not medical advice and it does not diagnose anything. It shows where a number sits against published ranges; what your result means for you depends on your lab, your ferritin, your other results, your history and your doctor.
MedlinePlus prints a normal iron saturation of 15% to 45% for women and 20% to 50% for men. Mayo Clinic Laboratories prints 14% to 50% for adults, and Cleveland Clinic calls 20% to 50% normal. Mayo uses under 16%, or under 20% where there is inflammation, to screen for iron deficiency. Over 45% is where it says hereditary hemochromatosis often sits.
How to use it
If your iron panel prints a saturation (“% saturation”, “Iron saturation”, “Transferrin saturation” or “TSAT”), type it and pick the ranges for women or men. If it does not, switch to “Iron and TIBC” and type both from the same report, in the same unit. The checker then works the % out by the formula the labs print. You see where it sits against all three sources’ lines, drawn one above the other, and each source’s own sentence where your % crosses a line it draws. It does not diagnose anything.
What the saturation is
Cleveland Clinic: “Transferrin saturation (TSAT) is a blood test that shows the percentage of transferrin that’s carrying iron.” Transferrin is the protein that carries iron in the blood. The TIBC is all of its iron seats, and the saturation is the share that are filled. Mayo Clinic Laboratories: “Transferrin is generally only 25% to 30% saturated with iron.” The lab does not measure it directly. Mayo’s formula is “Percent saturation = (Iron/TIBC) x 100”, and Cleveland Clinic prints the same: “TSAT = (Serum Iron / TIBC) x 100.” A serum iron of 75 and a TIBC of 300 make 25%.
The lines the sources draw
| Source | Women | Men |
|---|---|---|
| MedlinePlus | 15–45% | 20–50% |
| Mayo Clinic Laboratories | 14–50% | 14–50% |
| Cleveland Clinic | 20–50% | 20–50% |
MedlinePlus: “Iron saturation: Males: 20% to 50%; Females: 15% to 45%”. Mayo Clinic Laboratories (test SFEC) prints “PERCENT SATURATION 14-50%”. The CDC’s NHANES lab manual prints the same for adults: “Iron saturation, Serum, adult (calculated): 14-50%”. Cleveland Clinic: “Normal ranges are generally between 20% and 50%. Some labs have slightly different ranges.” So 17% is inside two lines and under the third, and 48% for a woman is above MedlinePlus’s line and inside the other two. “Most labs also provide a reference range so you know what they consider “normal.”” Your report’s range is the one that applies.
What the sources say at each line
Under 20%: Mayo Clinic Laboratories says “Percent saturation less than 16% is generally used to screen for iron deficiency, but a threshold of 20% is used in the presence of inflammation.” Cleveland Clinic says “Levels below 20% may mean iron deficiency anemia, malabsorption or chronic inflammation.” The CDC manual: “In iron deficiency anemia the TIBC is elevated and the transferrin saturation is <15%.” Over 45%: Mayo says “Percent saturation often exceeds 45% in hereditary hemochromatosis and 90% in advanced iron overload states.” Over 50%: Cleveland Clinic says “Levels higher than 50% typically mean iron overload (hemochromatosis) or a liver condition.” In both directions, Mayo: “Iron concentration and percent saturation decrease with iron deficiency and increase when iron is in excess.” Cleveland Clinic: “But one result outside the normal range doesn’t necessarily mean you have a health problem.”
Ferritin comes first
For the question most readers of this site bring, “is my iron low?”, Mayo Clinic Laboratories is plain: “However, serum ferritin is a much more sensitive and reliable test for demonstration of iron deficiency.” Read the saturation beside a ferritin result, not instead of one. The Ferritin Level Checker places a ferritin result, and the Serum Iron Level Checker and the TIBC Level Checker read the two lines the % is made from.
Before the blood draw
Cleveland Clinic: “You typically don’t need to prepare for transferrin saturation. But your provider may ask you to avoid eating or drinking the morning of the test.” The serum iron in the formula moves through the day. Mayo Clinic Laboratories: “The intraindividual day-to-day variation of iron and iron saturation is approximately 25% to 30%.” Mayo’s preparation for its iron panel is: “For 24 hours before collection, patient should not take iron-containing supplements.” Ask the person who ordered the test before changing anything you take.
Worked examples
- 28%, woman (the page’s example): inside all three lines, and near Mayo’s “25% to 30%”.
- 17%, woman: inside MedlinePlus’s 15–45% and Mayo’s 14–50%, under Cleveland Clinic’s 20%. Mayo’s under-20% inflammation sentence applies.
- 17%, man: under MedlinePlus’s 20% for men and Cleveland Clinic’s 20%, inside Mayo’s 14–50%.
- Iron 60 and TIBC 450: 60 ÷ 450 × 100 = 13.3%, under all three lines, with Mayo’s screening sentence and Cleveland Clinic’s under-20% sentence.
- 62%, man: above all three lines, with Mayo’s 45% sentence and Cleveland Clinic’s 50% sentence.
Common mistakes
- Reading the saturation as an amount of iron. It is a share. A low iron with a low TIBC can give an ordinary-looking %. Ferritin is the stores test.
- Mixing units in the formula. The iron and the TIBC must be in the same unit. The % itself has no unit.
- Typing a fraction. A report that prints 0.25 means 25%.
- One line taken as the line. The three sources’ lines differ by up to 6 points at the bottom; your lab prints its own.
- Taking iron before the test. Mayo asks for 24 hours without iron-containing supplements.
Frequently asked questions
What does low iron saturation mean?
Mayo Clinic Laboratories uses a saturation under 16% (under 20% with inflammation) to screen for iron deficiency. Cleveland Clinic: levels below 20% “may mean iron deficiency anemia, malabsorption or chronic inflammation”. Ferritin is the test that settles it, with your doctor.
What does high transferrin saturation mean?
Mayo: saturation “often exceeds 45% in hereditary hemochromatosis and 90% in advanced iron overload states”. Cleveland Clinic: levels over 50% “typically mean iron overload (hemochromatosis) or a liver condition”. One result outside the range does not necessarily mean a health problem.
What is a normal transferrin saturation?
MedlinePlus prints 15% to 45% for women and 20% to 50% for men. Mayo Clinic Laboratories prints 14% to 50% for adults, and Cleveland Clinic calls 20% to 50% normal. Your lab’s printed range is the one your doctor uses.
How is transferrin saturation calculated?
Serum iron divided by TIBC, times 100. Mayo prints “Percent saturation = (Iron/TIBC) x 100” and Cleveland Clinic prints “TSAT = (Serum Iron / TIBC) x 100.” Both numbers must be in the same unit.
Is iron saturation the same as TSAT?
Yes. MedlinePlus calls it iron saturation, and labs print “% saturation”, “Transferrin saturation” or “TSAT”. Cleveland Clinic lists it as “Transferrin iron saturation” too.
Is a 17% iron saturation low?
It depends on whose line: it is inside MedlinePlus’s range for women (15–45%) and Mayo’s (14–50%), but under Cleveland Clinic’s 20% and MedlinePlus’s 20% for men. Mayo’s screening line is 16%, or 20% where there is inflammation.
The whole panel at once — every line on one screen, and whether iron + UIBC = TIBC and the saturation add up: the Iron Panel Reader. More iron and blood-count checkers: the Transferrin Level Checker, the UIBC Level Checker, the Hemoglobin Level Checker and the Iron Tablet Timing Planner.
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This is not medical advice, and nothing here diagnoses or treats anything. It shows where a number sits against published adult lines and quotes what the sources say at them. Your lab’s own range, your ferritin, your other results and your doctor decide what it means. Some links on this site are affiliate links: I buy what I review at full price, and a commission never changes a verdict.