Thyroid UK
84,407 members99,412 posts

T3 dose confusion

At long last my Cynomel 25mcg order arrived after taking ages plucking up the courage to go ahead without GP support.

I'd really appreciate some advice on dosing. I'm currently taking 150/150/125mcg levo with TSH 0.34 (0.35-5) and T4 15.3 (9-24) on the 29th Jan 2015. I've been feeling very hypo similar to how I was when diagnosed 5 years ago. The GP refuses to test T3 and the consultant doesn't believe in T3!!

I'm gluten free and supplementing with Vit D3 and selenium due to antibodies. I am planning to take 25mcg a day split into 2 doses and reduce the levo to 100mcg daily?

I'd appreciate your views/ advice on what to do and when in terms of blood tests and how long it takes to work etc etc

Many thanks in advance,


8 Replies

I would change slower because if you reduce to 100 and take 25 mcg T3, you won't know what's exactly going on. Try 125/6.25 for at least 2 to 3 weeks. This will raise your fT3 and may not actually affect you fT4.

If you feel as though this is not working as well, then go 125/12.5. Your fT4 will go up and your fT3 will go up.

But you have no baseline fT3 recorded so you don't know what it is. You don't know if it's in the 3s or the 4s or the 5s right now. Which is why I suggest going slower.


That's good to know - the last T3 I had done was last April when referred to the endocriniologist, I can't find the numbers but I do remember it being at the bottom end of the range, and I still feel now like I did then


...great minds think alike :-)


You have not posted a result for the FT3. I think it would be good to have that test done. Your dose of T4 could be raised - before you begin to think of adding T3 into the mix. This is just non-medical me being cautious. :-)

Have you had your levels of Ferritin - Folate - Iron - B12 - VitD checked ? They need to be OPTIMAL for the current thyroid hormones to work efficiently....or even for when you add the T3.

Are you monitoring your pulse and temperature whilst on T4 ? It is a very good way of keeping track of things - and good training for when you are on T3. The pulse and temperature are a non-scientific - but good way of knowing when you are on an adequate dose.

Once you introduce T3 the TSH will be suppressed - the FT4 even lower and the FT3 must be below the upper limit of the range. You can have the FT3 tested privately through Thyroid UK....

Am not anti-T3 - it is not a quick fix and you need to tread carefully. I would take just one quarter of a pill twice a day to begin with - and only introduce more when your body has fully adjusted.....a quarter at a time.

1 like

I agree with Marz. Given you T4 dose is quite high but your fT4 is only 15, it looks as though you may have some problem with absorption as well. Which is why I"ve suggested leaving at 125 and adding only 6.25 for a while. It's once a day and it leaves you the possibility of increasing to 6.25 twice per day after a few weeks.

But as Marz says, where's the vitamin D, folate, ferritin, B12 results? Also if you need to get them done, ask for vitamin A as well.

Check your diet for magnesium. If it's deficient, you need to supplement this as well.


Methinks time for an overhaul - vit D was low last year and am supplementing, B12 I recall was 1200, one thing's for sure the GP won't allow these blood tests - it's such a fight to get them to believe you still feel rubbish! Thanks folks


Girlpower, you can order private blood tests from Blue Horizon and Genova via

I agree with Gabkad and Marz, it is better to start low ie a quarter of a tablet, 6.25mcg, added to 125mcg Levothyroxine as a little T3 can go a long way and it is easy to overmedicate. If symptoms don't improve in 3-4 weeks you can up dose to 2 x 6.25mcg.

1 like

Thanks folks for your helpful thoughts!


You may also like...