Thyroid UK
84,083 members99,057 posts

Is it ok to have low T4 if you're on T3 only?

I'm moving from a combination of T4 and T3 to (hopefully) T3 only. T3 is definitely working for me a lot better than T4 mentally and physically.

My last T4 result was 10 (range 9-21) and so my endo doesn't want me to change much more T4 into T3 because then my T4 may/will drop below the reference range. However I would be happy to go below the reference range because levothyroxine does help me a little but not a lot. I also wonder if it may be creating too much reverse T3.

But T4 is converted into T3 inside some organs so maybe I would be better off taking some T4 and not going T3 only? Or can the cells in these organs use the synthetic T3 in the T3 pills?

I'd just like to try T3 only. It may not be best for me but I'll never know unless I try it and so far taking an equivalent amount of T3 to T4 has been far superior for me each time I've increased the T3 and lowered the T4. I still have some symptoms, they could be connected to my sleep and anxiety problems but they could be helped by going T3 only.

Any thoughts?

Thanks xx

7 Replies

yes it is normal to have next to '0' level of fT4 if you are on T3 only.

I have been on T3 only since last year in May so nearly 10 months and my fT4 is non existant as my thyroid is suppressed (I take 150mcg daily).


There are many who are on T3 only for years and years and do well, some return to use some T4 some to use NDT, many stay on T3 only 'forever', whatever 'suits you'


Thanks, good to know :-)


Hi I know my endo ,is brilliant and keeps up with all the latest research.She thinks T4 and T3 is best but if T4 not tolerated, then, she uses T3 or even armour ( T4 and T3) ,what ever she thinks is best for her patient.



You and NBD are very lucky to have two Endos who can prescribe 'out of the box'.


I too have a fantastic endo and even though my TSH level is too small to measure and my T4 level is also below the lab-range, the fact that I'm feeling fine on the T4/T3 combination I have experimented with myself to get the optimum result, is enough for him to permit me to continue on this regime. He continues to monitor me as it is quite unconventional which, of course, avoids being discharged back into the care of GPs who haven't got a clue! Win-win all round!!! :-)



Is your Endo NHS? If so, please can you email me details? I have a VERY short list and am hoping to expand it! :-) Thanks!




Hi Louise,

I have just read your reply re Endos on the NHS and wonder if you could send me an up to date list. I live in Northamptonshire and have an older list from you but wonder if you have a more recent one, as I am looking for a good Endo after being with the same one for 7yrs and not getting well. After finally being allowed T3 added to my T4 and managing to up the dose over 2yrs to 60 mcg, this Endo has now left and a new one has halved my T3 because I still have symptoms, instead of increasing. He did this without even talking to me so I am now looking to find a new Endo who will help me to find the right dose of T3 and maybe allow me to use T3 only.

I have been undertreated for many years and can't do much outside the home, as I feel so exhausted and unable to much activity as I lack energy, especially on this new low dose of T3 I have been brought down to.. from 60 mcg to 30 mcg. I felt I needed an increase of T3 but the Endos at that hospital would not increase and decided to reduce it by half, without any real reason. I am now looking for a new Endo who will consider T3 only, as I think this is the only treatment that will work for me in higher doses than I was on and without the T4.

Can you email me please with any names of Endos who will help me in my search to get well after 30 yrs of being under treated and tired out. I have no quality of life and it has got worse over the last 5yrs, since I was forced to leave my job and have become a recluse, unfortunately.

Thank you... Sylvia ...


You may also like...