Thyroid UK

Opinions on FT3 result please

I posted a question recently about having diarrhoea in the morning and got some really useful answers. In the end I decided it must be related to the levothyroxine dosage so reduced it from 100 mcg to 75 mcg and that seems to have helped a bit. After a week on 75 mcg I did a private blood test and the results are:

TSH 0.33 (0.27 - 4.2)

FT4 21.0 (12.0 - 22.0)

FT3 4.1 (31. - 6.8)

I wanted my TSH to be low but probably that's too low. In May 2013 it was 2.85 (0.25 - 4.0) and FT4 was 20 (12.0 - 22.0). No FT3 because that was NHS.

Previous private FT3 results are July 2010 4.0 (3.0 - 6.2) and Oct. 2012 4.2 (3.1 - 6.8).

Is my current FT3 of 4.1 significant in the light of the TSH and FT4?

7 Replies

Hi - I think that those blood tests won't be very accurate, as you have had them taken after only 1 week on the reduced dose. I think blood tests take 4-6 weeks to settle after a dosage change. That said, I think that your fT3 looks rather low - I need mine to be over 5 to feel well. Is there any chance you could add in some T3? xx


Yes, I see what you're saying about the accuracy of the tests. I had originally intended to do the test the day before I reduced the dose, to see if the dose might be too high, but there was a delay in sending the test kit.

I'm grateful for the comment about the T3 as I was wondering if it was too low. I'm due to see my GP on Monday so will take the results and ask about T3.


Your free T4 is high... are you taking levo AND T3? You may have a conversion issue

Have you taken the adrenal questionnaire? if you have high score here the T4 may make you feel worse not better.. have a look

Let us know what you get


Yes I agree about a possible conversion problem with a high fT4 and a low fT3. My endo agreed to some T3 when I pointed out to him that the 50mcg of thyroxine he prescribed me, caused my fT4 to go up, but my fT3 to drop. I am now on Armour, which contains T3, and feel a million times better than on T4 only. Good luck with your doctor. xx


me too.. armour is great....I feel like myself again after a long time

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No, I'm just taking levo which is why I was wondering about the T3. I've had a look at the adrenal fatigue questionnaire and I don't think that's the problem but thanks for the suggestion

Will let you know what GP says..


Saw GP yesterday and he thinks FT3 is OK. I will keep an eye on it - he was quite happy to accept Blue Horixon test. However it was obvious from what he said that he does know about adding T3 and I think would do it if he thought it necessary. For the moment, he agrees perhaps my dosage went too high too quickly (various factors - the fact I should have been treated years ago (different GP), hot weather coinciding with the increase to 100 mcg, my age (66)) so has reduced it to 75 mcg for 3 months, which I'm happy with. I'm prepared to try that and see what happens.


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