I second all of this. Reason being i went through this myself a couple years back. I had random bloodwork done and my creatinine was through the roof high. I went to see a nephrologist and he did the bloodwork again, also ordered a CT and ultrasound of my kidneys.
Function of kidneys were excellent. However the creatinine was still high. not as bad for second round of blood panels but still high. I kept up on my bloodwork for approximately 3 months and eventually my creatinine went back to normal.
Since then i've continued to get bloods done every 3 months on my own with a nephrology panel like rhyno said. All good now!
However if the Doc is suggesting a biopsy, i'd definitely strongly consider it brother.
Keep us posted