Thyroid UK
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thyroid levels in healthy individuals?

I never had my thyroid levels tested before doctors suspected a problem, so I have no idea what my FTs looked like before I turned hypothyroid. I was wondering if anyone had labs before developing a thyroid problem, and could tell me what they looked like?

It is often said that, on meds containing T3, your FT3 levels should be at the top of the range, and your FT4 levels midrange. However, when your thyroid works just fine, your FT3 levels are not higher than your FT4 levels, are they? Or is the idea that we should take into account inadequate conversion of T4 to T3?

3 Replies

Hi thecat

I doubt the vast majority of the nation have ever had a thyroid gland blood test when they were young and healthy. None of us, I reckon know what the result was, even if we had one as we wouldn't have asked, I think.

When the blood tests were first developed they took samples from people and some might well have been hypo without having symptoms yet but were included in the 'ranges'. I was never even tested despite having loads of symptoms as nowadays, symptoms have become 'a thing of the past' due to the new blood tests introduced around the 60's.

Also, around the country labs use different types of equipment which produce different ranges, that's why we always ask members for the ranges when they post their results.

So, as you see, it is not easy to answer your question. Someone might have a better suggestion than mine.


Desiccated thyroid has a T4:T3 ratio of about 4:1. Humans secrete it at about 10:1. So people on desiccated show a higher FT3 than FT4, which reflects the formula of their medication. If you were to take a medication that truly mimicked the human gland, I would suspect that your FT3 and FT4 would be balanced, and both would be somewhere in the upper half of a reference range. People taking only levo usually show higher in range T4 and lower in range T3, again an expected effect of their medication.


I asked one of the endoprats I saw about this!! I asked directly how he knew my bloods were out of kilter when I had never been tested when well!! Of course I got a stock answer which seems to be parroted by most doctors 'We have ranges of course'. I'm sure they are taught at university that the TSH test is the be all and end all........


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