Thyroid UK
89,165 members103,681 posts

Wondering about levels?

I've been treated for hypothyroidism for about 20 years and have never really felt any benefit from the treatment. I am on 75mcg of thyroxine daily and my levels are:

Serum TSH level 0.88 mu/L (0.35 - 5.00mu/L)

Serum free T4 level 18.9 pmol/L (9.00 - 24.00pmol/L)

Serum free T3 level 4.4 pmol/L (3.50 - 6.50pmol/L)

Without boring people with too many details, my friend and I (both the same age) are trying to get fit by cycling which we've been doing since April. She's improved hugely whereas I, although I have improved, am miles behind her in terms of fitness now. I tire very easily and am wondering if my thyroid might be to blame although the comment on the lab report above says the levels are satisfactory?

5 Replies

diamondial The lab report will say satisfactory because the results are within range, but they're not optimal. Your T4 to T3 conversion is poor, this is illustrated by FT4 : FT3 ratio is 18.9 : 4.4 which is 4.29 : 1

Good conversion takes place when the ratio is 4 : 1 or less, some say 3 : 1. Also, your FT4 is 66% through it's range but your FT3 is only 30% through it's range. They should both be in balance nearer the top of the range.

Exercise is using up what little T3 you have and there's not much to replace it. This is the reason why you're tiring easily and you're not doing well compared with your friend.

You could ask for an increase in Levo which will increase your FT4 and will, to some extent, increase your FT3. But because your conversion isn't good, you would be better off adding some T3 to your Levo.

However, before considering that, you need to make sure that all your vitamins and minerals are at optimal levels because thyroid hormone can't work uness they are. You need the following tested

Vit D




If you post results then members can comment and suggest supplements if necessary.

Also, supplementing with selenium l-selenomethionine helps conversion of T4 to T3, the usual dose is 200mcg daily.


Oh thank you so much for such an informative reply SeasideSusie. I will ask for a blood test as you suggest and will meantime buy some of the selenium you mention. I will post again once I have had the blood test and results. Thank you again - I am extremely grateful!


I now have my results - in fact a myriad of them which I don't understand! I can't see any mention of Vit D but, as I say, there are loads of results which are incomprehensible to me including a full blood count. All results are marked as satisfactory. Those I do understand are:

Serum Ferritin is 137ug/L Range 15.00 - 250.00ug/L

Serum Folate is 9.8ug/L Range 2.00 - 17.00ug/L

Plasma Vitamin B12 408ng/L Range 200.00 - 900.00ng/L

I wasn't sure whether to start a new post or reply here and hope this is okay but please let me know if not. Are these levels fine?



You could start a new thread so it goes to the top of the current page then members can comment. G

The results here show your Ferritin is good, it should be half way through it's range, which it is.

Folate should be at least half way through range, yours is half way

B12 - I have read (but not researched so don't have links) that BCSH, UKNEQAS and NICE guidelines recommend:

"In the presence of discordance between test results and strong clinical features of deficiency, treatment should not be delayed to avoid neurological impairment."

And an extract from the book, "Could it be B12?" by Sally M. Pacholok:

"We believe that the 'normal' serum B12 threshold needs to be raised from 200 pg/ml to at least 450 pg/ml because deficiencies begin to appear in the cerebrospinal fluid below 550".

"For brain and nervous system health and prevention of disease in older adults, serum B12 levels should be maintained near or above 1000 pg/ml."

I keep my level at around 1000. Sublingual methylcobalamin lozenges 1000mcg are what's needed if you wish to self supplement, along with a good quality B Complex to balance all the B vitamins.

Vit D says something like 25-hydroxyvitamin D or similar


Many thanks SeasideSusie. I'll start a new post with all my results. I can't see any mention of Vit D unfortunately. I'll get hold of the lozenges and B complex vitamins tomorrow as you suggest.


You may also like...