Type the UIBC (unsaturated iron binding capacity) from your iron panel. You see it against the ranges three laboratories print — the CDC’s NHANES manual, Labcorp and Children’s Minnesota — and, if you add the serum iron from the same report, the TIBC and transferrin saturation by the lab’s own formulas. Ferritin, your lab’s own range and your doctor have the last word.
220 mcg/dL is
Inside all three printed ranges 220 mcg/dL = 39.4 µmol/L
220 mcg/dL: inside the CDC NHANES manual’s 112–347 mcg/dL for adults (Roche method), inside Labcorp’s 111–343 mcg/dL (its sample report), inside Children’s Minnesota’s 70–310 mcg/dL for women (Abbott method).
That is inside all three printed 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 the labs say, in their words
- The CDC manual: “In an average person about one-third of transferrin’s binding capacity is utilized. The remaining binding capacity is referred to as the unsaturated iron binding capacity (UIBC). The sum of serum iron and UIBC represents the total iron binding capacity (TIBC).”
| Lab (method) | Women | Men |
|---|---|---|
| CDC NHANES manual (Roche) | 112–347 | 112–347 |
| Labcorp sample report | 111–343 | 111–343 |
| Children’s Minnesota (Abbott) | 70–310 | 69–240 |
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.
The CDC’s NHANES lab manual prints an adult UIBC range of 112 to 347 µg/dL, and Labcorp’s sample report prints 111 to 343. Children’s Minnesota, which uses a different method, prints 70 to 310 µg/dL for women and 69 to 240 for men. The UIBC is the iron-binding room still free on transferrin, and adding the serum iron to it gives the TIBC.
How to use it
Type the UIBC line from your iron panel and say whether it is printed in mcg/dL (the same number as µg/dL) or µmol/L. Then pick the ranges for women or men. You see where it sits against each lab’s printed range, with the three drawn one above the other. If the same report prints a serum iron, type that too, in the same unit. You then get the TIBC by the CDC manual’s formula, “FE + UIBC = TIBC”, and the transferrin saturation by its “(FE/(FE+UIBC))*100”. Each is placed against the ranges MedlinePlus and Mayo Clinic Laboratories print. The checker does not diagnose anything: it places a number and quotes the labs.
What UIBC measures
Iron travels in the blood on a protein called transferrin, and each transferrin molecule has seats for iron. The CDC manual: “In an average person about one-third of transferrin’s binding capacity is utilized. The remaining binding capacity is referred to as the unsaturated iron binding capacity (UIBC). The sum of serum iron and UIBC represents the total iron binding capacity (TIBC).” So the UIBC is the empty seats, the serum iron is the filled ones, and the TIBC is all of them. Labcorp’s iron panel (test 001321) reports all four lines together: “Percent of saturation; serum iron; total iron binding capacity; unsaturated iron binding capacity”.
The ranges the labs print
| Lab (method) | Women | Men |
|---|---|---|
| CDC NHANES manual, adults (Roche) | 112–347 µg/dL (20.1–62.1 µmol/L) | 112–347 µg/dL (20.1–62.1 µmol/L) |
| Labcorp sample report | 111–343 µg/dL (19.9–61.4 µmol/L) | 111–343 µg/dL (19.9–61.4 µmol/L) |
| Children’s Minnesota (Abbott) | 70–310 µg/dL (12.5–55.5 µmol/L) | 69–240 µg/dL (12.4–43.0 µmol/L) |
The CDC’s NHANES 2019–2020 procedure manual lists the assay as run by the University of Minnesota’s Advanced Research and Diagnostic Laboratory on a Roche Cobas analyzer. It prints “UIBC, Serum, adult : 112-347 ug/dL”. Labcorp’s range comes from the sample report it publishes for its iron panel, a 2018 report for a 32-year-old man. That is the interval its report printed, not a separate published table. Children’s Minnesota’s handbook page uses Abbott’s Alinity reagents and prints “UIBC Male 69 – 240 mcg/dL Female 70 – 310 mcg/dL”, with no age band. The two Roche-type ranges agree within 4 µg/dL, while the Abbott-method lab’s edges are much lower. That is why a result of 280 for a man is inside two ranges and above the third. Your own report prints the range its method uses. To convert µmol/L we use iron’s atomic weight (1 µmol/L = 5.5845 µg/dL), the same factor as the TIBC checker. This checker is for adults.
UIBC, TIBC and saturation: one panel, three views
The CDC manual prints both formulas its laboratory system uses: “The calculation for TIBC is executed in StarLIMS: FE + UIBC = TIBC” and “The calculation for iron saturation is executed in StarLIMS: (FE/(FE+UIBC))*100”. Its adult ranges for the two calculated lines are “TIBC, Serum, adult (calculated): 250-400 ug/dL” and “Iron saturation, Serum, adult (calculated): 14-50%”. Those are the same numbers Mayo Clinic Laboratories prints. MedlinePlus prints TIBC by sex (149–492 µg/dL for women, 171–505 for men) and saturation by sex (15–45% and 20–50%). So a UIBC of 280 with a serum iron of 40 is a TIBC of 320 and a saturation of 12.5%. The TIBC Level Checker works the same panel from the TIBC line, and the Iron Saturation Checker takes a printed saturation percentage.
What moves it
Because the UIBC is the TIBC minus the serum iron, it rises when the TIBC rises or the iron falls, and it falls the other way. The CDC manual: “In iron deficiency anemia the TIBC is elevated and the transferrin saturation is <15%.” “Anemia of chronic disorders, malignant tumors and infections is characterized by low serum iron and low TIBC.” Its method notes list what can throw the test itself. “In patients treated with iron supplements or metal-binding drugs, the drug-bound iron may not properly react in the test, resulting in falsely low values.” “Oxytetracycline causes artificially high UIBC values at the tested drug level.” “If the patient’s serum iron exceeds the binding capacity of the transferrin, a negative UIBC value will result.” And: “In the presence of high ferritin concentrations (>1200 ug/L) the assumption that serum iron is almost completely bound to transferrin is not valid.”
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 UIBC beside a ferritin result, not instead of one. The Ferritin Level Checker places a ferritin result against the NIH’s and the WHO’s lines.
Before the blood draw, if you take iron
The CDC manual’s note on iron supplements is above. Mayo Clinic Laboratories’ patient preparation for its iron panel is: “For 24 hours before collection, patient should not take iron-containing supplements.” Children’s Minnesota: “Patient should be fasting. Morning values are 30% higher.” Ask the person who ordered the test before changing anything you take.
Worked examples
- 220 µg/dL, woman (the page’s example): inside all three printed ranges.
- 280 µg/dL, man: inside the CDC manual’s 112–347 and Labcorp’s 111–343, above Children’s Minnesota’s 69–240. Add a serum iron of 40 and the TIBC is 320 (inside both TIBC ranges), with a saturation of 12.5%, under both saturation ranges.
- 90 µg/dL, woman, serum iron 180: under the two Roche-type ranges, inside the Abbott one. The TIBC is 270 and the saturation is 66.7%, above both saturation ranges.
- 40 µmol/L, woman: inside all three ranges once they are converted to µmol/L (20.1–62.1, 19.9–61.4 and 12.5–55.5).
Common mistakes
- Reading UIBC as an iron level. It is the room left on transferrin. A high UIBC goes with LESS iron on board, not more.
- Using another lab’s range. UIBC ranges differ by method much more than most lab values: 69–240 on one analyzer, 112–347 on another. Your report’s own range is the one that applies.
- Mixing units. The UIBC and the serum iron must be in the same unit before they are added or divided.
- Taking iron the morning of the test. The CDC manual says iron supplements can make the result falsely low, and Mayo asks for 24 hours without them.
- Skipping the ferritin. Mayo calls ferritin the more sensitive and reliable test for iron deficiency.
Frequently asked questions
What is a UIBC blood test?
It measures the unsaturated iron binding capacity: how much more iron the transferrin in your blood could carry. The CDC manual: “The remaining binding capacity is referred to as the unsaturated iron binding capacity (UIBC).” It is usually part of an iron panel with serum iron, TIBC and saturation.
What is a normal UIBC?
It depends on the lab’s method. The CDC NHANES manual prints 112 to 347 µg/dL for adults and Labcorp’s sample report prints 111 to 343. Children’s Minnesota, using Abbott’s method, prints 70 to 310 for women and 69 to 240 for men. Your report’s printed range is the one your doctor uses.
What does a high UIBC mean?
It means a lot of transferrin’s iron seats are empty: either the TIBC is high, the serum iron is low, or both. The CDC manual: “In iron deficiency anemia the TIBC is elevated and the transferrin saturation is <15%.” Ferritin is the test that settles it, with your doctor.
What does a low UIBC mean?
Few seats are empty: the TIBC is low, the serum iron is high, or both. The CDC manual names “Anemia of chronic disorders, malignant tumors and infections” as “characterized by low serum iron and low TIBC”. It also notes that iron supplements can make the result falsely low.
How do you calculate TIBC from UIBC?
Add the serum iron: the CDC manual’s laboratory system computes “FE + UIBC = TIBC”. A UIBC of 250 and an iron of 80 give a TIBC of 330, in the same unit.
What is the difference between UIBC and TIBC?
The TIBC is all of transferrin’s iron seats, and the UIBC is only the empty ones. The serum iron fills the rest: the CDC manual says “The sum of serum iron and UIBC represents the total iron binding capacity (TIBC).”
Should I stop iron before a UIBC test?
The CDC manual says iron supplements can give “falsely low values”, and Mayo Clinic Laboratories asks for 24 hours without iron-containing supplements before its iron panel. Ask whoever ordered your test.
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 TIBC Level Checker, the Ferritin Level Checker, the Hemoglobin Level Checker and the Iron Tablet Timing Planner.
Read next
- How to get rid of anemia? The best 4 products
- The best vitamins for women at 30+
- Multivitamins for adults: how to choose
This is not medical advice, and nothing here diagnoses or treats anything. It shows where a number sits against published adult ranges and quotes what the labs say about it. 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.