Introduction
Transferrin saturation (TSAT) shows how much iron your blood is carrying. Transferrin is a protein that moves iron around your body. TSAT tells you what percent of that carrying space is filled with iron.
Enter your serum iron and your total iron binding capacity (TIBC). The calculator divides iron by TIBC and multiplies by 100. You can use mcg/dL or µmol/L for both values.
You can also add your serum ferritin. Ferritin shows how much iron your body has stored. Adding it gives you a fuller picture. Low TSAT with low ferritin often points to iron deficiency. High TSAT with high ferritin can point to iron overload.
Pick your biological sex so the tool uses the right cut-off. A TSAT under 20% is low for males. Under 15% is low for females. Over 50% is high for anyone.
The calculator shows your result on a color-coded scale, explains what it means, and walks you through each step of the math. Use it to understand your lab report, then talk to your doctor about what to do next.
How to use our TSAT Calculator
Enter your biological sex, serum iron, and TIBC from your blood test. You can also add ferritin. The calculator shows your transferrin saturation (TSAT) as a percent, tells you if it is low, normal, or high, and shows the math and charts behind it.
Biological Sex: Pick male or female. This sets the low TSAT cut-off used to read your result (under 20% for males, under 15% for females).
Serum Iron Concentration: Type the serum iron value from your lab report. Then pick the unit that matches your report: mcg/dL or µmol/L.
Total Iron Binding Capacity (TIBC): Type your TIBC value and pick its unit, mcg/dL or µmol/L. This is how much iron your transferrin can carry in total.
Serum Ferritin (optional): Type your ferritin value and pick ng/mL or pmol/L. Adding it helps the tool tell apart low iron stores, functional iron deficiency, and iron overload.
Press Calculate to see your TSAT percent, where it falls on the range bar, and a step-by-step solution. Press Reset to clear your numbers and start again.
What Is Transferrin Saturation (TSAT)?
Transferrin saturation, or TSAT, is a blood test result that shows how much iron your blood is carrying. Iron does not float freely in your blood. It rides on a protein called transferrin. TSAT tells you what percent of those "seats" on transferrin are filled with iron.
The Three Lab Values Behind TSAT
- Serum iron: how much iron is in your blood right now.
- TIBC (total iron binding capacity): how much iron your transferrin could hold if every seat were full.
- UIBC (unsaturated iron binding capacity): the empty seats left over. It is just TIBC minus serum iron.
TSAT is serum iron divided by TIBC, times 100. So if your iron is 95 mcg/dL and your TIBC is 330 mcg/dL, about 29% of the seats are full.
What the Numbers Mean
Normal TSAT is usually about 20% to 50%. Doctors often use a lower cut-off of 15% for women and 20% for men.
- Low TSAT means your blood is not carrying much iron. This is a common sign of iron deficiency, which can cause tiredness, pale skin, cold hands, and shortness of breath.
- Normal TSAT means iron is moving through your blood the way it should.
- High TSAT (over 50%) means transferrin is very full. This can happen with iron overload or a genetic condition called hemochromatosis, where the body stores too much iron.
Why Ferritin Matters Too
Ferritin is the protein that stores iron, like a pantry. TSAT shows iron that is moving; ferritin shows iron that is saved. Looking at both gives a clearer picture:
- Low TSAT + low ferritin = true iron deficiency (the pantry is empty).
- Low TSAT + normal or high ferritin = functional iron deficiency, often seen with long-term illness, infection, kidney disease, or inflammation. There is iron, but the body cannot use it well.
- High TSAT + high ferritin = possible iron overload.
Things That Can Change Your Result
Iron levels move up and down during the day and are usually highest in the morning. Iron pills, vitamin C, recent meals, birth control pills, pregnancy, and infections can all shift the numbers. Blood is often drawn in the morning after fasting for the most reliable result.
Note: TSAT is one clue, not a diagnosis. Always go over your lab results with a doctor, who will look at your symptoms, your full blood count, and your other iron tests before deciding what to do.