This is a question that comes up occasionally from thyroid patients.
If someone is on one type of T3 (or even NDT), and it is being taken in several divided doses per day, but the patient needs to change brands for whatever reason, what is the best way to go about this?
Well, do not wait until one type of medication runs out before switching over to the new brand. Swapping all doses at once is not advisable, as the brands may have different strengths and may even have unwanted side effects.
This advice I always give to thyroid patients is to pick the last dose of the day and swap to the equivalent dose size in the new brand.
It might not work the same way. Give it at least a few weeks to assess it, and adjust the new dose strength in tiny amounts in order to make it work in the same way as the previous brand.
At the end of this last-dose-adjustment-process, you will know the equivalent strength of the new brand compared to the old brand.
You can now safely adjust one of the other doses and fine-tune if you need to.
Proceed in this way until all the doses are switched over.
The main thing to do is to start early, well before your old brand has run out.
I hope this helps.