This has been my understand as well. I have CKD and my doctors have always been chill about it as long as I stop taking it about a week before having blood work done.

EDIT: I don't do 25g though... sounds like a lot...

You're lucky your doctor is aware of it. I've had several who did not understand, and insisted creatine must be dangerous if it elevated creatinine levels, and/or didn't understand the effects.