Enter the Serum Iron and Total Iron Binding Capacity into the calculator to determine the Transferrin Saturation. This calculator can also evaluate any of the variables given the others are known.
Related Calculators
- Friedewald Equation Calculator
- Atherogenic Index Calculator
- Ckd Protein Calculator
- Ldl-C/Apob Ratio Calculator
- All Health and Medical Calculators
Transferrin Saturation Formula
Transferrin saturation (TSAT) estimates how much of the blood’s iron-transport capacity is currently occupied by iron. It is calculated by comparing serum iron with total iron binding capacity (TIBC) and expressing the result as a percentage.
TSAT = \frac{SI}{TIBC} \cdot 100| Variable | Meaning | Typical Unit |
|---|---|---|
| TSAT | Transferrin saturation | % |
| SI | Serum iron concentration | µg/dL |
| TIBC | Total iron binding capacity | µg/dL |
Important: serum iron and TIBC must be entered in the same unit system. If the units do not match, the percentage will be incorrect.
How to Calculate Transferrin Saturation
- Measure the serum iron value.
- Measure the total iron binding capacity (TIBC).
- Divide serum iron by TIBC.
- Multiply the result by 100 to convert it to a percentage.
This calculator can also solve for a missing variable when the other two are known.
SI = \frac{TSAT \cdot TIBC}{100}TIBC = \frac{SI \cdot 100}{TSAT}Calculation Example
If serum iron is 80 µg/dL and TIBC is 320 µg/dL, then:
TSAT = \frac{80}{320} \cdot 100 = 25\%That means 25% of the available iron-binding sites are occupied by iron at the time the sample was collected.
What the Result Means
TSAT is commonly used as part of an iron study panel. By itself, it does not diagnose a condition, but it helps show whether circulating iron appears relatively low, adequate, or increased in relation to transport capacity.
- Lower TSAT may be seen when available circulating iron is reduced.
- Higher TSAT may be seen when a larger share of transferrin is carrying iron.
- Interpretation is strongest when combined with other labs such as ferritin, hemoglobin, hematocrit, red cell indices, and markers of inflammation.
Why TSAT Matters
Transferrin is the main protein that transports iron through the bloodstream. Measuring saturation helps estimate whether iron delivery may be limited or excessive relative to binding capacity. This is useful in evaluations involving:
- possible iron deficiency
- possible iron overload
- anemia workups
- monitoring response to iron therapy
- chronic disease states where iron handling may be altered
Factors That Can Affect the Number
TSAT can shift based on biology, timing, and lab conditions. Consider the full clinical context before drawing conclusions from a single value.
- Recent iron supplementation can temporarily raise serum iron and TSAT.
- Time of day may affect serum iron measurements.
- Inflammation or illness can change how iron is stored and transported.
- Liver disease, hemolysis, or transfusions may alter iron-related results.
- Non-fasting vs. fasting collection can influence comparability between tests.
Common Input Mistakes
- Entering serum iron and TIBC in different units.
- Using transferrin directly when the calculator expects TIBC.
- Rounding too early before multiplying by 100.
- Interpreting a single abnormal value without the rest of the iron panel.
Quick Interpretation Notes
- A TSAT result is a ratio, not a direct measure of total body iron stores.
- Ferritin often helps answer the separate question of how much iron is stored.
- Two people can have the same TSAT but different overall iron status depending on ferritin, blood counts, symptoms, and underlying conditions.
Frequently Asked Questions
Can transferrin saturation be greater than 100%?
Physiologically, saturation above 100% does not make sense. If that appears, common explanations include unit mismatch, data entry error, specimen issues, or an unusually low reported TIBC relative to serum iron.
Is transferrin saturation the same as ferritin?
No. TSAT estimates how much iron transport capacity is currently being used, while ferritin reflects iron storage. They answer different questions and are often interpreted together.
Why can the result change between tests?
Serum iron can vary with timing, recent supplementation, diet, illness, and laboratory conditions. Repeat testing is sometimes needed for a clearer picture.
Should this calculator be used for diagnosis?
This calculator is best used for calculation and education. Medical interpretation should be based on the full iron panel, symptoms, health history, and clinician review.
