Too much synthroid

[Eshep]

I just have question that came to mind, if you had your synthroid increased way too quickly, will it convert to reverse t3? Why wouldn’t it just make you hyper instead?

[helvella Administrator Thyroid UK]

Too much levothyroxine can result in hyper-like effects.

Most of the known effects of hyperthyroidism seem to be due to excess T3. So regardless how much T4 you take, it has to be converted to T3. That reduces the rate at which T3 can rise to the rate at which you can convert. Might still be too high!

The conversion process can switch from making T3 to instead making rT3. This is often seen as a way of managing excess T4. (My view is that we simply do not know enough!)

[greygoose]

It's not the speed at which you increase that causes it to convert to rT3, it's the level of your FT3. If that is too high, it will convert to more rT3 than T3. But, of course, if you increase too quickly, you will be at greater risk of ending up with your FT4 too high in range.