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Thyroid UK
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NHS V Medichecks (FT4)

Hi, I'm trying to get diagnosed central hypo. I've had everything tested on Medichecks and my FT4 is extremely close to being below range. I was going to show these results to my GP once it falls below range. However I'm feeling really worried as I've seen quite a few results on here where NHS FT4 has been significantly higher than Medichecks FT4 (taken at roughly the same time). And I'm sure doctors will want to retest.

Can anyone tell me if this has been the case for them?

7 Replies

In my experience NHS GPs always want to retest because they want to have the tests done by their own lab within the NHS remit so everything is easily signed off on for paperwork and funding, etc.


I've seen quite a few results on here where NHS FT4 has been significantly higher than Medichecks FT4 (taken at roughly the same time).

Has the reference range been the same for both tests?

I know Medichecks FT4 range is 12-22 by my GP's lab's range is 7-17 so you wouldn't be able to compare the actual result, only what percentage through the range they are.


Mostly they've been cases of, the Medichecks result being below range and the NHS result being low normal.

Here's a few examples:


healthunlocked.com/thyroidu... (This ones a longer read but OP posts that she has Free T4: 13.3 pmol/L [9 – 24 pmol/L] with an NHS endo, and later in the month FREE THYROXINE 12 pmol/L [12.00 - 22.00] with Medichecks)

healthunlocked.com/thyroidu... (NHS TSH 0.05 (0.3-4.2). FT4 23.3 (12-22)

MC TSH 0.051 (0.3-4.2). FT4 21.85 (12-22) Same day)

I know this is nitpicky but would make the difference between a diagnosis and no diagnosis for me. I'm not sure I want to put myself through the disappointment of my NHS retest coming back in range!

1 like

Your first example turned out that the member had Hashimoto's and that would explain the difference in the results, antibody activity will make results fluctuate.

Your second example, although so many results it's quite mind boggling, seems that the NHS results were non-fasting and most likely afternoon blood draw, were all showing a quite similar TSH of around 3ish. The Medichecks result was from an early in the day, fasting, blood draw which gave a TSH over 4 which would be expected. And as FT4 has a circadian rhythm too then there will be some difference between an early morning and an afternoon blood draw.

Your third example is the same member as your first example, and it transpired she has Hashimoto's healthunlocked.com/thyroidu... which, as mentioned, would account for the differences in the results.

As for trying to get a diagnosis of central hypothyroidism, you will probably find that a GP hasn't heard of it, and possibly not many endos either. Most endos are diabetes specialists so know little about the thyroid. You might need to gather plenty of research/articles about central hypothyroidism to get your GP to consider it then look for an endo who is a true thyroid specialist.


That's definitely reassuring, thank you for the response Suzie. It slipped my mind that FT4 has a circadian rhythm.

I do have a lot of research and I also have some NHS guidelines on interpreting low FT4/normal TSH results. Unfortunately my nearby hospital has quite a small endocrinology department and I doubt they have any pituitary specialists there. Can't really do anything about it either as I'm currently living in Wales. Fingers crossed...


I live in north Wales and the two endos (different hospitals) are both diabetes specialists.

If you email Dionne at tukadmin@thyroiduk.org she can send you a list of thyroid friendly endos then you can look up their specialities and make some enquiries. Ask on the forum for feedback from members too, you never know you might get lucky :)


I thought this link may be helpful. It's a pity doctors don't know very much except to look at the TSH and T4 and pronounce that their is nothing wrong when it is obviously not the case if clinical symptoms are also acknowledged. (they know none).






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