How to Lower Creatinine Levels & Improve Kidney Functions? Our body is designed in such a way that it excretes out the waste material after the work of the nutrients has been completed. For example creatinine, it is a waste product of protein metabolism and creatine phosphate in muscles. It is excreted out on a constant rate by the body. The rate of the excretion of creatinine could be used as an indicator to know about the kidneys health. If