What is the most reliable test to measure kidney function?  A fasting CMP measuring creatinine?  Results seem to be based on hydration and if fasting for 12 hour without fluids also cause creatinine to increase is this reliable indicator?  Should CMP be repeated with good hydration to be reliable?
Good Day, and thank you for being with Chat Doctor ! The best way to measure kidney function is to have your GFR measured. This is similar to a ct scan and is the gold standard.  I hope I have succeeded in providing the information you were looking for. Please feel free to write back to me for any further clarifications at: http://www.ChatDoctor .com/doctors/ Chat Doctor.  Best wishes