Thyroid UK
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Thyroid Ranges?

Who is it that comes up with the thyroid ranges and what data is this generally based on? Also when the ranges change are the actual values still the same? Just the range has changed through my treatment and I don't have a baseline to work from unless the values used are still the same and the goal posts have been widened?

Also how can someone be overmedicated with a suppressed TSH but the Free T3 and Free T4 are within range and there are no symptoms which would suggest being overmedicated?

4 Replies

"Also how can someone be overmedicated with a suppressed TSH but the Free T3 and Free T4 are within range and there are no symptoms which would suggest being overmedicated?"

Yep, I get that too!

Dr: You're over medicated

Me: In what way?

Dr: Your TSH is suppressed

Me: It's always been suppressed, but my FT4 is in range (as was my FT3)

Dr: You're over medicated

Me: But I still have residual hypo symptoms and no symptoms of being over medicated

Dr: You're over medicated

They are TSH obsessed, very few doctors will go against the "TSH must be in range" guidelines and don't take into account the free Ts or symptoms.

Sorry, I can't help about the ranges, they've changed in my area too but not massively.


Gsp177, the ranges are based on mean average population statistics local to the lab. If the analysis machinery and technique hasn't changed it may be that your results are interpreted within a broader or narrower range ie your TSH may have been 1.0 in range 0.35-5.0 and will still be 1.0 in a new range 0.27-4.20. The upper and lower limits shouldn't make any difference to you but they will to patients looking for a diagnosis.

It's only doctors who test and treat according to TSH levels who are likely to consider suppressed TSH equals overmedication. Unless FT4 and/or FT3 are over range in addition to suppressed TSH the patient isn't overmedicated.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.


Do bear in mind that the alternative to changing ranges is not changing them! Even when the lab has realised that they are wrong, or their technology has changed, or whatever else has happened.

For example, there has been a greater appreciation that the people used to set ranges should be free of anyone with known thyroid issues. This would tend to change the reference ranges but, on its own, would NOT change the result an individual would get.

An improved test that was less likely to be affected by interference from antibodies or other substances could well affect an individual's results as well as change the reference ranges.

A broad brush approach would be to suggest that if your result was top of range on a test, then it is likely to be top of range on a revised test/with a revised reference range. Unless the factors that have changed apply to the specific individual. (Similarly for bottom of range. Or middle.) That is, if your results were being affected by some antibodies, then cleaning up the test so it is not affected by them would change your result - possibly significantly.


I have noticed that some of the ranges for TSH that have been reported here recently have been lower (eg 0.3 to 4.5 instead of 0.5 to 5.5) than I was seeing a couple of years ago. Has anyone else noticed this?


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