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Thyroid UK
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Change to FT3 Normal Range

I had my private testing carried out by Blue Horizon in September 2016 which showed the normal range for FT3 to be 3.1-6.8. I found out today via another source that this range changed on 13 October 2016 to 4.2-6.9. Would have been a good idea for Blue Horizon to have informed those who used them for blood testing of this change.

Apparently the NHS specialist I first saw a few weeks back didn't know this because he said my FT3 result of 3.75 was in range with the pre-change Normal Range of 3.1-6.8!

4 Replies

Not sure why Blue Horizon would necessarily have to inform you, the range will be on the result sheet next to the test result.

The test where the range was different could have been done with a different lab, BH uses more than one lab.

I had results from BH ten days ago, and FT3 range was as it always has been when I've used them, 3.1-6.8

Who is this other source that told you the range was changed in October 2016? I have done 6 thyroid tests with BH since November 2016 and all of them had the FT3 range of 3.1-6.8, so I think your source has made a rather sweeping statement without looking into the facts.



There is no universal range for FT3 or other thyroid results. You should use the range the lab provides with your results. Your source may have had the range change in 2016 at the lab s/he uses but that doesn't affect other labs.


Thank you for letting me know Clutter.


In effect the range is that of the machine its tested on which is why you see many posts asking for the ranges. It's really guesswork without them.

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