This is a myth, its not bad for your kidneys. The reason this gets spread is because you will have higher levels of creatine in your urine if your Doctor tests your urine for kidney function, which indicates kidney disease.
However, If you reveal to that doctor that you're supplementing Creatine it will not be concern them.
However, If you reveal to that doctor that you're supplementing Creatine it will not be concern them.