Thyroid UK

Replacing some T4 with T3 - advice please?

Hi all,

I have had the DI02 polymorphism from one parent confirmed and after some help from this forum I have now ordered my T3 (25mcg tabs) and will be replacing some T4 and with T3 as soon as it arrives.

I did seek medical advice from a private endo but it looks like his approach would leave me undertreated and feeling really poorly quite quickly (thanks everyone who gave great advice and some really useful research materials!)

So, I'm going it alone and I just wondered if anyone can share how you went about adding T3 in. Did you just go Big Bang or add in incrementally?

I'm particularly interested in anyone' else with DI02 polymorphism's experiences as because we don't convert effectively I'm thinking it won't be a simple switch based on current T4 dose but will instead involve a lot of trial and error so any tips would be really helpful.

Finally, I will do some labs too in about 6 weeks but I am really planning to go by how I feel.

I am committed to being patient and I'm certainly not expecting results overnight but equally I don't want to delay progress or feel ill unnecessarily either.

Any ideas on how quickly I should be able to feel whether the dose is right, on track or way off?

Thanks in advance 😃


My last labs:

TSH 0.22

FT4 19.6

FT3 3.1

3 Replies

I haven't had a DIO2 test but think I might have a defect. However, you haven't said what levothyroxine dose you take at present.


Oh, sorry of course that would be helpful!

I take 125mcg per day



Introduce T3 slowly to see how well you tolerate it. Buy a pillcutter from any pharmacy and start by adding a quarter tablet (6.25mcg). You can increase to 12.5mcg split into two doses after 2 weeks if necessary. Hold at 12.5mcg for 6-8 weeks and have a FT3 test before increasing further.


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