Thyroid UK

Blood tests requested by gp included transferrin saturation index

Had blood tests today. Managed to get gp to do b12, ferritin and folate but noticed she had requested a transferrin saturation index. Has any one else had this? What's it for? On 150mcg of levothyroxine after tt and still feeling awful. In fact I think I'm getting worse. Hoping these tests show something. How long did it take anyone to get stable after a tt?

3 Replies

Transferrin saturation is one of the tests in the 'Iron studies' group of tests. There are probably lots of circumstances when this is an appropriate test, but I had it recently to try to rule out haemochromatosis!


Copied this from lab tests online:TIBC measures the total capacity of your blood to transport iron, and therefore reflects your body's iron stores. TIBC correlates with the amount of the protein transferrin in your blood. Transferrin is a protein that attaches iron molecules and transports iron to the blood plasma. Transferrin is largely made in the liver and regulates your body's iron absorption into the blood. While the two tests (TIBC and transferrin) are different, they measure essentially the same thing. Most laboratories only measure one or the other. A few laboratories are now measuring the number of sites on transferrin that are not already carrying iron; this is referred to as unsaturated iron binding capacity (UIBC). This number can be added to the serum iron to calculate the TIBC.


Hi This is the most important test as shows the absorption rate. If not absorbed, as in my case, however high the result it is useless. Mine on max treatment +vit C is still only 17%. means I have to have more on a script but in the end, just not good enough.

Best wishes,



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