Thyroid UK

Help with TSH and T4 results

Hi. I wondered if anyone can help me interpret my results?

I have had an underactive thryoid for a number of years and had been taking 125mcg thryoxine regularly. At a test in September my levels changed quite suddenly as follows:

TSH 45 (ref range 0.35 - 4.94)

T4 11 (ref range 0 - 19)

My GP told me my thryoid was now very underactive and to increase my medication from 125mcg to 150mcg. I did this and went for a re-test 6 weeks later. Results as follows:

TSH 0.19

T4 29

The GP said my thyroid was now going slightly the other way - slightly overactive and so told me to go back to my original dose of 125mcg. I did this and went for a re-test 6 weeks later. Results as follows:

TSH 0.05

T4 21.7

I have just spoken to my GP and she suggested that I drop the dose to 100mcg as it is still only slightly overactive. However, when I look at the figures it looks like it's slightly underactive to me. (as 0.05 is lower than the reference range of 0.35-4.94). Is she right to decrease my medication? Does this result suggest an underactive or overactive thyroid?


4 Replies

How do you feel? Was the original TSH .45 or 45. Seems like a dramatic change to me.

Looking at just the result 0.05 it would suggest a supressed thyroid result so technically overactive. But it needs to be looked at as a whole. I would personally say that you want to remain on the dose and ask to be tested again in 6 weeks and see what it says. Did you take your medication before it? Was it first thing in the morning?


I agree with Poppy03

The TSH is not an entirely reliable measure and the doctor shouldn't just use this solely. Also your T4 is only slightly over the top end of the range so this is not a problem, as long as you are not experiencing any symptoms of taking too much thyroxine.

If you feel ok on the current dose I'd try and stay on it. I made the mistake a few years ago when my t4 was similar to yours and I felt quite reasonable at the time, my GP gave me the choice to stay on the same dose or go down. Not knowing much about it all at that time I went down a dose. Big mistake! - I've not had a good day since despite going up again after 2 of weeks. Don't let your GP try and scare you as one did to me saying I would have a heart attack because I was taking too much medication!! Turns out after the bloods I was right and he wasn't! If you are not happy with the advice your GP gives you you can ask to be referred to an endocrinologist.

All the best

Rose x


I doubt it, but have they by any chance tested your FT3 levels? Also, have you been tested for anti-bodies?


This is link regarding TSH and Patients' Experiences : Suppressed to 0.5


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