Thyroid UK

Iron test confusion

I am trying to understand the logic behind iron blood tests. And need some help.

My results are:

Serum iron level: 16 ( 9 - 30 umol/L)

Serum transferrin: 28 ( 25 - 45 umol/L)

Transferrin saturation index: 0.29 (0.0 - 0.45)

Ferritine: 63 (15 - 150 ug/L)

I've read multiple times that to find out Transferrin saturation I need to divide iron by transferrin. If I do it I get following:


That looks like my transferrin saturation is higher than the upper range. Why the lab gives a different number then? And how to interpret it with the rest of the tests?

I would say :

Iron is only 33% along the range instead of 55 to 70%, this is low.

Serum transferrin is 15% of the way through the range, which is probably also low.

Ferritin has room to get higher.

And Transferrin saturation is a riddle for now.

My naturopath does not seem to see any problem in this picture. Would it be necessary to address low iron by supplementing, or something in this test is not correct?

4 Replies

Viv123 sorry you have had no replies, I for one, know nothing about iron.

Here's a former post which may be relevant...


Not that I know much about iron, but this site seems to be quite a lot better than many when it comes to iron:


one possibility for the discrepancy is that the transferrin is measured in umol/L rather than ug/L as the ferritin is - so it won't just be a question of dividing one by the other but converting the units as well.

There will be a fixed multiplier for doing this but I don't know what it is


thank you Gambit62. I found out that the right formula for units used in my blood test will be:

Transferrin saturation % = (iron umol/l x 100)/(transferrin umol/l x 2)

And here is formula of conversion of units if somebody needs:

transferrin (g/L) x 12.6 ==> transferrin (µmol/L)

found it here

Using this info I understood that my Transferrin saturation index was counted correctly: 0.29 (0.0 - 0.45)

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