I'm actually going the other way and already on tirz while wanting to add reta. From what I've read, keeping both low seems preferable. The main warning I've seen is that the two act on similar pathways, which could lead to dangerously low blood sugar. I use a CGM with alarms so I get notified right away if levels drop too far.
Right now I'm using 5 mg reta each week plus 0.5 cag and I'm hoping to bring in tirz, but I'm unsure what amount would be safe. Any dosing ideas or thoughts on side effects? I've searched the forum already but haven't come across the details I'm after.