Can you use Usnic Acid while on T3?
Yes. Watch your dosages, maintain a 40/40/20 diet and enjoy. You might want to consider something to combat muscle loss though with that combo.
I heard that while on Usnic Acid you should not have low carbs why?
Uncouplers hinder your body from effectively utilizing carbs to make ATP (energy). Thus, since your body is forced to be reliant on primarily fats, you would want to avoid ingested fats and hence force the body to utilize stored fatty acids. Make sense?