Joanna, the vet probably means to decrease the Tapazole to 1/4 tablet twice daily and not 1/2 tablet once daily. The second option would create spikes in the thyroid levels (because the medicine doesn't last for 24 hours in the body) and that is what you want to avoid.

I am not sure what the vet tech was referring to when she talked about the "kidney level", but you may find that once the Tapazole dose is decreased or you take the T131 route, the kidney damage will be stopped.

Please keep us posted on Tex's condition and your decisions.