Is the use of creatine bad for your kidneys?
Please check these topics first.
No! This is a myth. Excess creatine becomes creatinine which is then excreted via the kidneys. Kidney function is measured by glomerular filtration rate which shows how efficiently the glomerulus of the kidneys filters blood. Creatinine clearance was classically used as a measure of glomerular filtration rateusing a creatinine clearance test which involved measuring creatinine in blood and a timed 24 hour urine sample. Because this test takes 24 hours and has compliance problems it has been replace by plasma creatinine measurements which are then used to calculate creatinine clearance or estimated glomerular filtration rate (eGFR).
Creatinine is a remarkably non-toxic molecule but because it is used as a measure of kidney function unscrupulous supplement manufacturers describe it as toxic.
Medical biochemistry labs have several methods available to measure creatinine. The standard Jaffe method uses alkaline picrate.This has been in use for about a century and is cheap but it overestimates the creatinine concentration. It also has disposal problems since it is explosive and there have been lab accidents in which drains from lab sinks have exploded.