Thyroid UK
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How do the ranges affect the results?

Can anyone please tell me in what way the ranges affect the results? The reason I ask this is, do they re-calibrate their test equipment or something? Does that mean, for example, the same specimen could come up 0.5 in one lab and 1.0 in another? I had the vague idea that your own level would be absolute (give or take a margin for error). I live in a village with mainly older people in it - a fair number are under-active I think, or so it seems from talking to people. Would that skew the results? And if so, would sending to Blue Horizon, for example, give me a more realistic result? Suddenly it all seems to be a minefield!

5 Replies

It is a minefield.

It depends on many factors. Including which make of analysis machine and testing kit.

Supposedly this is then checked against a sample of people from the lab's area. That sample is supposed to exclude anyone other than fit, healthy people with no known thyroid issues. I think older people might be excluded on those grounds. I have seen rumour that some labs simply use the manufacturer's range and, unless something looks obviously wrong, do nothing more. That could be unfair. Any lab people able to verify what really happens?

Absolutely the same specimen could come up 0.5 in one lab and 1.0 in another. You would hope that if you plotted the value against the reference range for the lab and did the usual interpretation of where you are on the curve, it would represent a similar place. E.g. 10% from bottom, exact middle, etc. But you often see that "they" have tried to shoehorn the fairly complex distribution of TSH into a standard Gaussian (or "normal") distribution.

As to whether Blue Horizon are more realistic, I think it depends on why the variations occur in the first place. But even the lab behind Blue Horizon's tests is subject to the same fundamentals.

I feel that at first cut you have to see where you are on the lab's own reference range.



When i made ELISA kits which were for a range of autoimmune diseases and some for cancer the ranges were based off the strenght of the antibody solutions used and 100 normal samples ever wonder what happend to the samples you supply when you give blood(as in the three test tubes) whatever the blood bank doesnt use gets sold to companies like the one i worked for.

I can only assume a similar thing gets done in our hospital labs to set up the normal range.


Hi It is fine to have any bloods at different Labs, but you must always have the ranges, not just thyroid. That is because their assays are different. It is simpler with thyroid tests to try and use the same Lab, but not important.

Best wishes,



I've never had the tests done before, so it was a magical mystery tour to me. The doctor has never been willing to give me the figures, let alone the ranges!

I've just got my results from Blue Horizon - guess what - they didn't include the ranges! I've phoned them and they have apologised and are sorting it out. So long as they are doing it right, I'l just go to them every 6 months to reassure myself that my T3 is OK since the doctor will not even consider it. Would you believe, he told me it is pointless as T3 is inactive!

Hence I'm taking responsibility for my own health , since all he has done is try to destroy it. I have gone from a relatively healthy working woman to an invalid since I changed to this doctor - not out of choice but due to a house move.

I really appreciate your input and advice, Jackie, thanks again.


Gp just ask the receptionist, they have to check with a GP( any around) and give you a print out there and then. I have a terrible GP practice,Ogre in charge! the first time I did have to say, well it is my blood. Now it is accepted practice. My hospital admissions, emergency every few weeks, I ask which ever doc has the results, or even the nurses, when they have come down on the PC, but then. you must ask for their ranges, as they tend not to put them on as of course, very famiar with them. Same applies for OP but if not asked phone the consultant`s secretary. Also always make sure you have copies of consultants letters to the GP, that is a rule now under freedom of info ( ask the doc or sec) the blood is not, that is because it is your blood! The most enlightened docs write to you with a copy to GP. Your body!Useful.If we could have done that years ago, I would have known my thyroid needed treating 20 years early, GP kept it secret, the ogre!When I used to have to go into 2 local hospitals, while ago, horrible places, patients did not matter and caused 2 arrests by not listening to other docs and me. Even then I had bloods by asking a few times!

I use Blue Horizon as My NHS can no longer do FT3. I think that must have been true as never had any without ranges from them.

Yes it gets to the stage, I well know that you have to be very proactive, I am not normally aggressive but have learnt. I also always choose my own consultants, with care. I cannot change practices ( GP`s) as so ill, so many drugs, it would not work for me. Just have to watch and ignore them.

Do try and get the correct treatment, Let me know how you do, PM me if you like, click on my name



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