Log in
Thyroid UK
93,726 members107,744 posts

Help with results please, low t4 on T3/T4 treatment


I've been on 50mcg levo and 20mcg liothyronine for a few weeks having been on 100mcg levo for a few months previously.

I have defo felt better with the T3 but not anywhere near optimal. The last week I've felt myself going downhill again.

Anyway, my ft4 has dropped a lot since the alteration. GP has upped the T4 to 75mcg and retest in 6 weeks.

I'd hoped by now I'd be getting close to being properly well so this is a bit disheartening!

12 Replies


FT4 has dropped because you replaced 50mcg with 20mcg T3. Increasing to 75mcg will raise FT4 and FT3. Bear in mind that symptoms can lag behind good biochemistry by a few months.


My ft4 hadn't been below 10 before even without treatment which I guess is why it's concerned me. I was hoping to increase my T3 dose a bit as I'm not sure how well I convert (I have the dio2 gene) but GP happy as it is.

I'm being impatient I suppose.


It's not a very high dose = T4+T3 to around 110mcg of levo. When T3 is added into T4, the T4 will be lower due to you taking T3.

It took me about six or seven years to get were I am today. Some are lucky and some have to tread a weary road but can get there with advice and support. There was no forum when I became ill but Thyroiduk.org.uk led the way forward, for which I am eternally grateful and symptom-free.


I can't imagine dealing with this without online support.

I've always felt undermedicated, even though my TSH is suppressed now.


You might need a combination to feel an improvement, i.e. some T3 added to T4. Some GPs wont prescribe and the BTA frowns on it for some reason especially if it should help patients and after all it is the only Active thyroid hormone. levo is inactive and has to convert to T3.

It is a big learning curve, isn't it. Not as easy as going to the doctors and coming out with a prescription then a few weeks later whatever we've complained about has disappeared and we feel well.


I am on a combination t4 and T3 🙂


My ferritin is below what I'd like, around 50 I think. I do have hashis.

I'll give this increase a while to kick in then. It's so long winded isn't it. I just want to feel good again.


As far as we know, the only reason for having T4 at all is to convert it into T3, so if you are taking T3, the T4 drops as it isn't needed, so your results are what you'd expect if you are taking T3. TSH is low because your pituitary reckons that there's enough thyroid hormone and doesn't needto tell your thyroid to produce more

If you started on T3 because you weren't converting T4 to T3 well, there's not much point raising your t4 dose as it won't get converted any better than it was before - I'd add a little more T3 and make sure that my B12, folate and ferritin were optimum. If you've only been on that dose of T3 for a few weeks, I'd stick with it (not raise) as it takes a while for your body to "catch up" with your thyroid.


Yes, I've been trying to find out what else T4 is used for but no one seems to be able to tell me. Surely it must have some use - but I have more hair loss when my FT4 is higher ...


Interesting, I was wondering if I need to worry about the t4 but it's a little odd it's the lowest it's ever been, pre and post meds. I would like my ft3 to be closer to 6 really.


I've never been able to fathom it. My FT4 was around 16 on T3 only, then I raised my T3 by a quarter of a tablet and it dropped to 10 - there seems to be a certain point at which your body decides it just doesn't need the T4 any more (or something) and it only takes a tiny change to trigger it.


I didn't realise if you take T3 then your T4 drops. That may explain my results (low T4 & TSH but T3 OK.) Does it matter if your T4 is low if your T3 is fine?


You may also like...