Thyroid UK
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Query about blood test reference ranges

Hi, does anyone know how a reference range can be so different in other labs. I had my Ferritin levels done along with other bloods as I had all the symptoms of anaemia but the doctor said I was fine. The ref range was 12.00 - 300.00ug/L and mine was 36 so it didn't seem too bad. My dad has just had his done in another town and the ref range was 30.00 - 365.00ug/L. This isn't just a small difference and if I'd had mine done at my dads doctors I would have only just been in range. How can this be right? I have now started taking iron as when I got the printout my Haematocrit was low as well but still the doctor said I was fine.

3 Replies

I think you are falling into a trap.

If you had yours done at your dad's doctors, your result would likely NOT have been 36.

There are lots of reasons for these reference ranges varying.

If you have two thermometers - one a modern Celsius one, the other an old Fahrenheit one - and you put them right next to each other, then the numbers they show will be different. The coldest and hottest temperatures that you feel comfortable at will be different numbers. Think fo that as the reference ranges for the thermometers.

Both thermometers work. Both are accurate. But the reference ranges are different. And the current temperatures shown are different.

It would be much, much better if all labs had the same reference ranges. For now, they do not, although there is some effort to move in that direction.

To get back to the ferritin, if your result had been 12.00 at your lab, you SHOULD have expected the result to be 30.00 at you dad's doctors. I.e. if at bottom of range at one lab, it should be at bottom of range at another lab.

Sorry if all I have done is confuse!



Thanks Rod, I knew that some labs use for instance ug/L and others use say iu/L or whatever but when they are both measured in the same units I would have thought the measurement within those units would be the same.

Thanks for clarifying it for me.


No - unfortunately. Even with the same units they end up showing different numbers all too often.

I was trying to illustrate that they can diverge.


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