Thyroid UK
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Why doesn't my T4 go up?

my latest results show tsh, 0.71 (range 0.20-4.50) and my T4 is 9.4 (range 7.0-17.0)i cant say i feel wonderful on this reading, still extremely tired, seem to be in a low mood all the time.

all the readings are in range, but the T4 range goes up to 17 so i dont feel on my optimum dose yet, it seems i can get my tsh really low but cant get my T4 up any higher, i was wondering if anyone could advise or has experienced this before, thanks,

5 Replies

Obvious suggestion is that you are not yet taking enough! How much are you taking?

In my view, TSH could be allowed to go down further.

I assume you do take your thyroxine well away from food,drinks other than water, supplements and other medicines?



I'm on 175 mcg, I take it at night just before bed

Doctor argued with me saying my tsh was fine and really would like to reduce the dose.


Well I do not agree with them! We see quite a seizable proportion of people needing doses higher than GPs may be comfortable prescribing. But 175 is not even that high if it is full replacement. (If you were fine, then they could be OK.)

However, it is always worth looking at the other things. Have you been tested for:

vitamin B12



vitamin D

... and did you get the results?



Hi thanks for your reply, yes I got the results and continue to take b12, frolic acid and b6 didn't understand the vit d results and the iron I took till the level was right but last bloods showed that red blood count was low. I thought 175 was high? Might ask again then, should the t4 be over the 17? Thanks for any advice you can offer


I really don't think we see anyone on levothyroxine only who is happy at a point well below half-way up the FT4 scale. That would be 12 on the range you posted! And you are at 9.4. :-(

Many find that their FT4 needs to be somewhere near top of range.

175 is not a tiny dose, but some people are on more than 300 micrograms. The British National Formulary says that the "usual maintenance dose 100–200 micrograms once daily" - but that is far from saying no-one needs more.

Low RBC:

A low RBC count may indicate anaemia, bleeding, kidney disease, bone marrow failure (for instance, from radiation or a tumour), malnutrition, or other causes. A low count may also indicate nutritional deficiencies of iron, folate and vitamin B12.


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