I wonder if your psychiatrist doubts if your bipolar medications are the problem, especially since you are not taking Lithium. I'm not saying I think one way or the other, though. I'm not qualified to know. However, it's odd that your GP doesn't know and your psychiatrist doesn't want changes. The nephrologist may be the very best idea and end this apparent show down between your gp and pdoc. Are you 100% sure your bipolar medications are the culprits? There are many more common causes for kidney damage.

I have mild kidney damage, and likely from Lithium. I have hypothyroidism, too. Probably from Lithium. When my psychiatrist discovered my high creatinine level (a frequent test for Lithium users because of its possible affect on kidneys) he referred me to a nephrologist. He does not order a creatinine level now that I'm not on Lithium. My nephrologist does, but not because of my current medications, but to see if my kidney damage from past use of Lithium is improving or worsening. It's improving.

You mentioned some test results numbers. They must be from some other type of kidney function test than I'm familiar with or are a different representation. My creatinine test results are usually more like 1.2 to 1.6, etc.