thyroid function test results: hi you've helped... - Thyroid UK

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thyroid function test results

sueoathall profile image
16 Replies

hi you've helped me a lot before, can you help me again please?

I've had my blood test results back. What do you think?

Stupidly I can't remember whether I took my thyroxine before I went!

My results are as follows,

T4 17.4 (range 12.00 to 22.00 pmol/L)

T3 3.7 (range 3.10 to 6.80 pmol/L)

TSH 0.05 (range 0.27 to 4.20 mu/L)

My GP wants me to reduce my dosage of 125mg to 100mg on alternate days. I was told to do this a few years ago, but someone told me you shouldn't do that. That you should have the same dosage every day.

I'm really not sure what to do.

Many thanks

16 Replies
SeasideSusie profile image


Stupidly I can't remember whether I took my thyroxine before I went!

Unfortunately, that's not very helpful when interpreting your results.

If you took your Levo before the test then you have a false high FT4.

If you left the advised 24 hour gap between last dose of Levo and test then your FT4 result is accurate and quite low in range at only 54%. Most people on Levo only tend to feel best when FT4 and FT3 are in the upper part of their ranges.

So, the important question is

* How do you feel?

Your GP wants to reduce your dose on the basis of your low TSH which is wrong. TSH is not a thyroid hormone, it's a pituitary signal to the thyroid. The thyroid hormones are FT4 and FT3 and it's these that tell us what we need to know, and out of the two FT3 is the most important because T3 is the active hormone that every cell in our bodies need. Over range FT3 can suggest overmedication, low in range FT3 tends to cause symptoms.

FT4 and FT3 should be more or less balanced and yours aren't as FT4 is 54% through range and FT3 is only 16.22% through range. This suggests that you don't convert T4 to T3 very well and the cause of this could be low nutrient levels. It would be helpful to have the following tested:

Vit D




If these levels are optimal then it would suggest that your conversion is poor and you may need T3 added to your Levo. Come back with test results and ranges and we can comment.

Resist any suggestion of lowering your Levo, it's unlikely to make a significant difference to your TSH but it will lower your FT4 and FT3 levels which will make you symptomatic of hypothyroidism.

The following article may help you to convince your GP not to reduce your dose:

Dr Toft, past president of the British Thyroid Association and leading endocrinologist, states in Pulse Magazine (the professional magazine for doctors):

"The appropriate dose of levothyroxine is that which restores euthyroidism and serum TSH to the lower part of the reference range - 0.2-0.5mU/l. In this case, free thyroxine is likely to be in the upper part of its reference range or even slightly elevated – 18-22pmol/l. Most patients will feel well in that circumstance. But some need a higher dose of levothyroxine to suppress serum TSH and then the serum-free T4 concentration will be elevated at around 24-28pmol/l. This 'exogenous subclinical hyperthyroidism' is not dangerous as long as serum T3 is unequivocally normal – that is, serum total around T3 1.7nmol/l (reference range 1.0-2.2nmol/l).*"

*He recently confirmed, during a public meeting, that this applies to Free T3 as well as Total T3.

You can obtain a copy of the article by emailing Dionne at

print it and highlight question 6 to show your doctor.

sueoathall profile image
sueoathall in reply to SeasideSusie

thank you so much for your lengthy reply. Very interesting.

I will look into it . Thanks again

fuchsia-pink profile image

If you are on T3 meds, yes it's really important to take the same dose every day, because it has a very short half-life. Levo, though, is a storage hormone, so it's perfectly fine to have different doses on different days.

BUT your GP is just looking at TSH, which is suppressed. S/he doesn't seem to have noticed your actual thyroid hormones ... free T4 is 54% through range, so not brilliantly high, and free T3 is only 16.2% through range - so you are a VERY long way from being over-medicated and would probably benefit from an increase in meds ... and would probably feel quite a lot better if you can get a referral to a T3-friendly endo and a trial of lio, as your T3 result shows you don't convert at all well.

It can take a while to get a referral. Step 1 is to get an increase in levo (25 mcg a day or alternate days) while you research likely endos. Get the list from Dionne at Thyroid UK - - and put up a new post to see if anyone can recommend someone near-ish to you.

You don't have to see the nearest person, but must obv be reasonably convenient - and they don't have to accept you as a patient ...

Good luck x

sueoathall profile image
sueoathall in reply to fuchsia-pink

Thanks Fuchsia. I did get T3 over the Internet a few years ago but my source dried up. Thanks for the tip about T3 friendly endo. I will try that . Thanks so much

Jazzw profile image

Given your FT3 is only just above the bottom of the reference range, it’s fairly obvious to me you need a dose increase.

I really wouldn’t reduce my dose if I were you.

sueoathall profile image
sueoathall in reply to Jazzw

Thanks Jazzw

galathea profile image

Dont think i would be reducing anything with those results. Plenty of room for a thyroxine increase, your t3 levels are low. Can tell you now that your doc is trying to medicate you using Tsh. There is no chance of them getting you better using only the tsh... :-(. Stand your ground and tell the doc that yourresults for ft4 and ft3 could be improved. X

sueoathall profile image
sueoathall in reply to galathea

thank you

SlowDragon profile image

As your Ft3 is rock bottom you very likely have low vitamin levels

Essential to regularly retest vitamin D, folate, ferritin and B12

What vitamin supplements are you currently taking

When were vitamin levels last tested

Do you have Hashimoto’s, (autoimmune thyroid disease) diagnosed by high thyroid antibodies

Are you on strictly gluten free diet

Refuse to reduce dose of levothyroxine

Ask GP to test vitamins (and thyroid antibodies if not been done in past)

If not on gluten free diet also request coeliac blood test too

sueoathall profile image

Thanks for your reply. I need to get all those tests done. Have been reducing my gluten consumption but not totally gluten free. I will follow your advice. Thank you

SlowDragon profile image
SlowDragonAdministrator in reply to sueoathall

Point out to GP that Ft3 is currently only 16% through range and that to be adequately treated Ft3 needs to be at least 60% through range

Therefore you won’t be reducing levothyroxine dose. Instead will be looking at improving conversion of levothyroxine into Ft3. Therefore ask GP to please test folate, ferritin, B12 and vitamin D

Come back with new post once you get vitamin results and ranges

If only eating small amounts gluten not probably worth getting coeliac blood test. (You need high gluten diet for 6 weeks before coeliac blood test) Just cut gluten out completely

sueoathall profile image
sueoathall in reply to SlowDragon

Thank you

SlowDragon profile image
SlowDragonAdministrator in reply to sueoathall

Before considering adding T3 we need OPTIMAL vitamin levels

Vitamin D via NHS postal kit £29

Folate, ferritin and B12 via GP or Thriva

sueoathall profile image
sueoathall in reply to SlowDragon

I'm waiting to see the doctor to get tests done. Thanks

SlowDragon profile image
SlowDragonAdministrator in reply to sueoathall

No point testing for coeliac if already on low gluten diet

If testing for coeliac you need to still be eating high levels of gluten

If trialing gluten free diet,it needs to be absolutely strictly gluten free

sueoathall profile image
sueoathall in reply to SlowDragon

Hi Slow Dragon , yeah I was referring to vitamin level tests. I won't get the coeliac test but will be more strict, Thanks for your help.

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