Transferrin Saturation

Transferrin saturation (TSAT) is a blood test that shows the percentage of transferrin that’s carrying iron. Transferrin is a protein that moves iron through your blood. Iron can’t move well on its own, so transferrin binds to it and helps it move where it needs to go.

Your provider may order a TSAT test with other iron blood tests to diagnose iron-deficiency anemia or excess iron. It can also help evaluate liver problems. The results are given as a percentage that shows how much transferrin is carrying iron.

High transferrin saturation may mean you have a condition, such as too much iron in your body (iron overload). Low levels may mean iron deficiency or low iron.

The test is also called:

• Transferrin iron saturation
• Percent transferrin saturation

How does the test work?

Iron from the foods you eat enters your bloodstream and attaches to a protein called transferrin. Transferrin carries iron to places that need it, like your bone marrow and muscles. The iron is then released for your cells to use.

TSAT is calculated by dividing the amount of iron (serum iron) in your blood by your total iron-binding capacity (TIBC) and multiplying by 100. TIBC measures how much iron your blood can carry. TSAT = (Serum Iron / TIBC) x 100.

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. Ask them if you’re unsure if you need to prepare. Transferrin saturation is often ordered with other iron blood tests because it helps provide a more complete picture of how iron is working in your body.

The test is a blood draw. Your provider will take a sample of blood from a vein in your arm. They will send the sample to a lab for analysis. The test should only take a few minutes, and you can go home right away.

What are the risks and side effects?

The only risks and side effects are those related to a blood draw. These are usually mild and go away quickly:

• Pain or soreness at the needle site
• Bruising where the blood was taken
• Dizziness or lightheadedness

What type of results do you get and what do the results mean?

It can take a few days to get your results. Transferrin saturation is calculated using other iron blood test results, which is why they’re usually ordered together. The calculation is done by dividing serum iron (the amount of iron in your blood) by total iron-binding capacity (TIBC) (the amount of iron your blood can carry) and multiplying by 100.

Your lab report will give results as percent transferrin saturation. It will give a number, followed by a % sign. Most labs also provide a reference range so you know what they consider “normal.” Always check with your provider about your results and what they mean for you.

Ranges for TSAT are typically:

• Normal range: Normal ranges are generally between 20% and 50%. Some labs have slightly different ranges.
• Low levels(<20%): Levels below 20% may mean iron deficiency anemia, malabsorption or chronic inflammation.
• High levels (>50%): Levels higher than 50% typically mean iron overload (hemochromatosis) or a liver condition.

Remember, your provider uses these results along with results from other iron tests (like a ferritin test) to understand your iron levels.

If the results are abnormal, what are the next steps?

If you have abnormal results, the next steps depend on if your results are high or low. It also depends on the results of other iron blood tests.

• Low TSAT: Your provider may order more tests to confirm low iron (iron deficiency). They could also look into other conditions that cause low iron. They may recommend an iron supplement and/or recheck your iron levels to see if they increase.
• High TSAT: Your provider will look into why you have too much iron. Common causes include certain genetic diseases, taking too much iron or problems with your liver. They could recommend treatment and recheck your iron levels again in several months.

Your provider will review your results together with other iron tests to figure out what’s going on and decide whether treatment or follow-up is necessary.