I use and suggest the "Crea Pure" versions that out now, have more purity and potency than the stuff coming out of China and elsewhere, I think CreaPure is out of Germany, you might want to google and do some reading. I use 5g in my preworkout and I think...I think...(HA) its why my bodyweight is up and so are my lifts. I told my GF today that everything is working in my favor that last two weeks after feeling like I was plateaued.
https://www.amazon.com/gp/product/B002DYIZEO/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1
As far as my Kidneys and many BB's do feel that Creatinie/Kidney can be false elevated with gym activity and/or Creatine use. After getting some high(er) tests there I started only doing bloods when I'm off 72hrs from the gym and Creatine and I make sure that I'm fasted 10hrs, water only, before my labs. Also the Creatinine test itself doesnt account for the increased muscle mass you/i/we are or maybe carrying...higher muscle mass = more creatinine in the system. More so high protein diet...a number of things should be factored in when looking at the Creatinine test results.